MLPAO MLA/T Certification Exam — Questions and Answers

Question 1: What is the principle of the antimicrobial susceptibility test using the Kirby-Bauer disk diffusion method?

Measuring the minimum concentration of antibiotic that inhibits growth
Measuring bacterial growth curves with and without antibiotics
Measuring zones of growth inhibition around antibiotic-impregnated disks on agar (Correct answer)
Detecting antibiotic resistance genes by PCR

Correct answer: Measuring zones of growth inhibition around antibiotic-impregnated disks on agar

The Kirby-Bauer method measures the diameter of growth inhibition zones around standardized antibiotic disks placed on Mueller-Hinton agar inoculated with a standardized bacterial suspension. Zone sizes are compared to CLSI (or EUCAST) interpretive criteria to classify organisms as susceptible, intermediate, or resistant.

Question 2: What is the clinical significance of a positive DAT (direct antiglobulin test/direct Coombs) result?

The patient has a hereditary spherocytosis
Immunoglobulin or complement is bound to the patient's red blood cells in vivo (Correct answer)
The patient has developed alloantibodies from a previous transfusion
The patient requires emergency group O negative transfusion

Correct answer: Immunoglobulin or complement is bound to the patient's red blood cells in vivo

A positive DAT indicates that IgG antibody or complement (C3d) is coating the patient's own RBCs in vivo, indicating immune-mediated RBC sensitization.

Question 3: A pleural fluid specimen has an amylase level of 1200 U/L (serum amylase 80 U/L) and a pH of 6.0. What conditions should be considered?

Simple parapneumonic effusion
Esophageal rupture (salivary amylase) or pancreatic pleural effusion (pancreatic amylase); the very low pH supports esophageal rupture (Correct answer)
Pulmonary embolism
Congestive heart failure

Correct answer: Esophageal rupture (salivary amylase) or pancreatic pleural effusion (pancreatic amylase); the very low pH supports esophageal rupture

Markedly elevated pleural fluid amylase (>3× serum or >upper limit of serum normal) occurs in esophageal rupture (salivary amylase type) and pancreatic disease (pancreatic amylase type). A pH of 6.0 is very low and strongly suggests esophageal rupture (gastric acid contamination). Amylase isoenzyme analysis differentiates salivary from pancreatic origin. Esophageal rupture is a surgical emergency.

Question 4: What is the function of a micropipette calibration check using gravimetric analysis?

To check the pipette tip for contamination
To verify the electrical calibration of the analyzer
To verify the pipette delivers the correct volume by weighing dispensed water (Correct answer)
To measure the viscosity of reagents

Correct answer: To verify the pipette delivers the correct volume by weighing dispensed water

Gravimetric calibration checks a micropipette's accuracy by weighing aliquots of distilled water dispensed at the set volume, using the known density of water (1.00 g/mL at 20°C) to calculate the delivered volume.

Question 5: Which laboratory method is used as the reference (gold standard) for diagnosing malaria?

PCR for Plasmodium species
ELISA for Plasmodium antibodies
Microscopic examination of Giemsa-stained thick and thin blood films (Correct answer)
Malaria rapid antigen test (RDT)

Correct answer: Microscopic examination of Giemsa-stained thick and thin blood films

Microscopic examination of Giemsa-stained thick and thin blood films is the reference standard for malaria diagnosis, allowing species identification and parasitemia quantification.

Question 6: A CSF specimen is collected in three tubes. Which tube should be sent to the microbiology laboratory for culture?

Any tube may be used for culture
Tube 1 — most likely to contain pathogens
Tube 2 — least likely to be contaminated with skin flora (Correct answer)
Tube 3 — largest volume

Correct answer: Tube 2 — least likely to be contaminated with skin flora

Tube 2 is sent for microbiology culture because it is least likely to be contaminated with skin flora from the puncture site, which is most likely to contaminate Tube 1.

Question 7: Which method is most commonly used for measuring serum glucose in clinical chemistry analyzers?

Folin-Wu method
Hexokinase method (Correct answer)
Ortho-toluidine method
Somogyi-Nelson method

Correct answer: Hexokinase method

The hexokinase method is the reference method for glucose measurement. It uses hexokinase to phosphorylate glucose to glucose-6-phosphate, which is then oxidized by glucose-6-phosphate dehydrogenase with production of NADPH, measured spectrophotometrically.

Question 8: A patient has anti-Jk(a) identified 3 years ago but the current antibody screen is negative. Can the electronic crossmatch be used?

Yes, since the current screen is negative
Yes, but only if two typings are on file
No — once a clinically significant antibody is identified, an antiglobulin crossmatch with antigen-negative units is always required, regardless of current screen results (Correct answer)
The patient needs fresh plasma exchange first

Correct answer: No — once a clinically significant antibody is identified, an antiglobulin crossmatch with antigen-negative units is always required, regardless of current screen results

A history of a clinically significant antibody (especially Kidd antibodies, which are known for evanescence) permanently disqualifies a patient from electronic crossmatch. Jk(a)-negative units must be selected and an antiglobulin crossmatch performed. This antibody history must be maintained in the blood bank records and communicated across institutions.

Question 9: A transfusion sample is received in the blood bank with a label that has the patient's name but no second identifier. What should be done?

Reject the specimen and request a new properly labeled specimen collected with bedside identification (Correct answer)
Add the missing identifier from the requisition
Process if the name matches the requisition
Process the specimen using the name alone

Correct answer: Reject the specimen and request a new properly labeled specimen collected with bedside identification

A specimen missing a required identifier (two independent identifiers are mandatory) must be rejected. A new specimen must be collected at the bedside with proper patient identification. No exceptions should be made, as mislabeled specimens are the most common cause of fatal transfusion errors. This policy must be enforced consistently.

Question 10: According to the Medical Laboratory Technology Act, 1991, who is permitted to use the title "medical laboratory technologist" in Ontario?

Graduates of a recognized medical laboratory technology program.
Any individual working in a medical laboratory for over five years.
Only members of the College of Medical Laboratory Technologists of Ontario (CMLTO). (Correct answer)
Individuals who have passed the CSMLS national certification exam.

Correct answer: Only members of the College of Medical Laboratory Technologists of Ontario (CMLTO).

The Medical Laboratory Technology Act, 1991, is a profession-specific act that governs the practice in Ontario. It explicitly restricts the use of the title "medical laboratory technologist" and its variations to individuals who are registered members of the College of Medical Laboratory Technologists of Ontario (CMLTO). While graduation and passing the CSMLS exam are typically requirements for registration, they do not by themselves grant the right to use the protected title in Ontario.

Question 11: A peritoneal fluid analysis from an ascites tap shows WBC 800/µL with 70% neutrophils, total protein 12 g/L, and a SAAG of 14 g/L. What does this indicate?

Peritoneal carcinomatosis
Spontaneous bacterial peritonitis (SBP) in a patient with portal hypertension (Correct answer)
Uncomplicated cirrhotic ascites
Secondary bacterial peritonitis

Correct answer: Spontaneous bacterial peritonitis (SBP) in a patient with portal hypertension

The high SAAG (14 g/L) confirms portal hypertension (cirrhotic ascites). The PMN count >250/µL (800 × 70% = 560 PMNs/µL) meets the diagnostic criteria for SBP. SBP occurs in cirrhotic patients when bacteria translocate from the gut. Low protein ascites (<10 g/L) is a risk factor for SBP. Treatment is empiric IV ceftriaxone or cefotaxime.

Question 12: A blood smear shows bite cells and Heinz bodies on a supravital stain. The patient recently started taking a sulfonamide antibiotic. What is the most likely diagnosis?

Hereditary spherocytosis
Iron deficiency anemia
Glucose-6-phosphate dehydrogenase (G6PD) deficiency with oxidative hemolysis (Correct answer)
Autoimmune hemolytic anemia

Correct answer: Glucose-6-phosphate dehydrogenase (G6PD) deficiency with oxidative hemolysis

Bite cells (degmacytes) result from splenic removal of Heinz bodies (denatured hemoglobin precipitates). This pattern triggered by an oxidizing drug (sulfonamide) is classic for G6PD deficiency. The deficient enzyme cannot generate adequate NADPH to maintain reduced glutathione, leaving hemoglobin vulnerable to oxidative damage.

Question 13: A medical laboratory technologist discovers that a co-worker has been consistently falsifying quality control results. What is the CMLTO's expected response from the discovering MLT?

Report the concern to management and/or the CMLTO as a professional obligation (Correct answer)
Ignore the situation as it does not affect patient care directly
Address the issue privately with the co-worker and take no further action
Document the observation without reporting

Correct answer: Report the concern to management and/or the CMLTO as a professional obligation

CMLTO Standards of Practice require MLTs to report serious concerns about the conduct of colleagues to appropriate authorities when patient safety or professional standards are at risk.

Question 14: In the context of phlebotomy, the antecubital fossa is a critical anatomical landmark. Which vein within this area is most commonly the first choice for venipuncture due to its size and stability?

Basilic vein
Cephalic vein
Median cubital vein (Correct answer)
Brachial artery

Correct answer: Median cubital vein

The median cubital vein, located in the antecubital fossa (the crease of the elbow), is the preferred site for venipuncture. It is typically large, well-anchored (less likely to roll), and less painful to access compared to the cephalic and basilic veins. The brachial artery should always be avoided during venipuncture.

Question 15: A medical laboratory professional is reviewing the daily quality control data for a glucose assay on a Levey-Jennings chart. The last five consecutive control values have all plotted on the same side of the mean, but are still within ±2 standard deviations. Which of the following does this pattern most likely indicate?

A random error has occurred.
The control material is contaminated.
The instrument is functioning optimally.
A systematic error is developing. (Correct answer)

Correct answer: A systematic error is developing.

This pattern, where consecutive data points are distributed on one side of the mean, is known as a 'shift' or 'trend'. It is indicative of a systematic error, suggesting a consistent bias in the measurement process. This could be due to issues like deteriorating reagents, a change in instrument calibration, or a new lot of controls. A random error would result in unpredictable data points, not a consistent pattern.

Question 16: What does a positive oxidase test indicate, and which clinically significant organism is oxidase-positive?

Presence of urease; Proteus mirabilis
Presence of coagulase; Staphylococcus aureus
Presence of cytochrome c oxidase; Pseudomonas aeruginosa (Correct answer)
Presence of catalase; Staphylococcus aureus

Correct answer: Presence of cytochrome c oxidase; Pseudomonas aeruginosa

The oxidase test detects the presence of cytochrome c oxidase, an enzyme in the electron transport chain. Pseudomonas aeruginosa is a clinically important oxidase-positive, gram-negative rod. The test uses a reagent (tetramethyl-p-phenylenediamine) that turns dark purple when oxidized by the enzyme.

Question 17: What is the significance of Auer rods found on a peripheral blood smear?

They indicate viral infection
They are pathognomonic for acute myeloid leukemia (Correct answer)
They suggest iron overload
They indicate vitamin B12 deficiency

Correct answer: They are pathognomonic for acute myeloid leukemia

Auer rods are needle-shaped, reddish-purple crystalline inclusions found in the cytoplasm of myeloid blast cells. They are pathognomonic (uniquely diagnostic) for acute myeloid leukemia and are never seen in acute lymphoblastic leukemia or benign conditions. Multiple Auer rods (faggot cells) are characteristic of acute promyelocytic leukemia (APL/M3).

Question 18: In the complement system, which pathway is activated by antigen-antibody complexes?

Classical pathway (Correct answer)
Lectin pathway
Mannose-binding pathway
Alternative pathway

Correct answer: Classical pathway

The classical pathway is activated by antigen-antibody (immune) complexes when IgG or IgM antibodies bind to C1q, initiating the complement cascade.

Question 19: A cord blood sample has a positive DAT with anti-IgG. The mother is group O Rh-positive and the baby is group A Rh-positive. What is the most likely cause?

Autoimmune hemolytic anemia in the newborn
Rh HDFN
ABO hemolytic disease of the newborn due to maternal anti-A (IgG) crossing the placenta (Correct answer)
Laboratory error

Correct answer: ABO hemolytic disease of the newborn due to maternal anti-A (IgG) crossing the placenta

The most likely cause is ABO HDFN. Group O mothers produce IgG anti-A and anti-B (in addition to IgM), which can cross the placenta and coat the fetal A or B red cells. ABO HDFN is usually mild but can occasionally cause significant jaundice requiring phototherapy. An eluate from the baby's cells would confirm anti-A.

Question 20: What is the purpose of an anaerobic culture and which specimen types should NOT be cultured anaerobically?

To grow fungi; blood cultures
To isolate viruses; tissue specimens
To isolate oxygen-sensitive bacteria; specimens from sites with normal anaerobic flora (stool, vaginal) (Correct answer)
To grow aerobic organisms only; throat swabs

Correct answer: To isolate oxygen-sensitive bacteria; specimens from sites with normal anaerobic flora (stool, vaginal)

Anaerobic cultures isolate bacteria that cannot survive in oxygen. Specimens from sites with normal anaerobic flora (stool, vaginal, oral) should not be cultured anaerobically because normal flora will overgrow pathogens. Appropriate specimens include normally sterile body fluids, deep tissue, and aspirates from closed abscesses.

Question 21: What is the significance of anti-K (anti-Kell) in prenatal testing?

Anti-K causes severe HDFN by both destroying fetal red cells and suppressing fetal erythropoiesis; monitoring differs from anti-D HDFN (Correct answer)
It is not significant in pregnancy
Anti-K only affects the mother
Anti-K is prevented by RhIg

Correct answer: Anti-K causes severe HDFN by both destroying fetal red cells and suppressing fetal erythropoiesis; monitoring differs from anti-D HDFN

Anti-K is the most significant non-Rh antibody in HDFN. Unlike anti-D, anti-K suppresses fetal erythropoiesis by targeting Kell antigen on erythroid progenitors, causing anemia without proportional hyperbilirubinemia. Middle cerebral artery Doppler peak systolic velocity (MCA-PSV) is used for fetal monitoring rather than amniotic fluid bilirubin.

Question 22: Which specimen collection error would falsely decrease measured serum calcium?

Hemolysis of the specimen
Collecting in an EDTA tube instead of a red-top tube (Correct answer)
Using a serum separator tube
Prolonged tourniquet application

Correct answer: Collecting in an EDTA tube instead of a red-top tube

Collecting blood in an EDTA tube (lavender top) for calcium measurement would give falsely decreased results because EDTA chelates (binds) calcium ions. EDTA is an anticoagulant that works specifically by removing calcium, which is essential for the coagulation cascade.

Question 23: A patient's urine shows many waxy casts, broad casts, and RTE cells. What does this suggest?

Normal urinalysis
Dehydration only
Acute urinary tract infection
Severe chronic renal disease with tubular damage and stasis (Correct answer)

Correct answer: Severe chronic renal disease with tubular damage and stasis

Waxy casts indicate prolonged urinary stasis in damaged tubules. Broad casts ('renal failure casts') form in dilated, damaged collecting ducts. Renal tubular epithelial (RTE) cells indicate active tubular injury. Together, these findings suggest severe chronic kidney disease with ongoing tubular damage and a poor prognosis.

Question 24: Excessive centrifugation speed or time is most likely to cause mechanical hemolysis, leading to a falsely elevated result for which of the following analytes?

Glucose
Potassium (Correct answer)
Chloride
Sodium

Correct answer: Potassium

Red blood cells contain a much higher concentration of potassium than blood plasma. When red cells are ruptured (hemolysis) by excessive mechanical force during centrifugation, this intracellular potassium is released into the serum or plasma, causing a significant and false elevation in the measured potassium level.

Question 25: The MHC class II molecules present antigen to which subset of T lymphocytes?

Regulatory T cells only
CD4+ helper T cells (Correct answer)
Natural killer cells
CD8+ cytotoxic T cells

Correct answer: CD4+ helper T cells

MHC class II molecules on antigen-presenting cells present exogenous peptide antigens to CD4+ helper T cells via the CD4 co-receptor, initiating the adaptive immune response.

Question 26: In clinical chemistry, what does the term 'hemolysis' refer to and why is it a concern?

Breakdown of red blood cells; it releases intracellular contents that interfere with assays (Correct answer)
Bacterial contamination; it degrades analytes
Lipid accumulation; it causes turbidity
Clotting of the sample; it reduces volume

Correct answer: Breakdown of red blood cells; it releases intracellular contents that interfere with assays

Hemolysis refers to the rupture of red blood cells, releasing intracellular contents such as potassium, LDH, and hemoglobin into the serum or plasma. This is the most common preanalytical error in clinical chemistry and can falsely elevate or decrease many analyte measurements.

Question 27: A urine specific gravity is measured at 1.010 using a refractometer at a temperature of 27°C. The refractometer is calibrated at 20°C. Each 3°C above 20°C requires adding 0.001 to the reading. What is the corrected specific gravity?

1.012 (Correct answer)
1.010
1.013
1.009

Correct answer: 1.012

Temperature difference = 27 − 20 = 7°C. Correction = 7°C ÷ 3°C × 0.001 = 0.0023 ≈ 0.002. Corrected SG = 1.010 + 0.002 = 1.012.

Question 28: What does an elevated reticulocyte count indicate?

Chronic disease
Iron deficiency
Bone marrow failure
Increased red blood cell production (erythropoietic response) (Correct answer)

Correct answer: Increased red blood cell production (erythropoietic response)

An elevated reticulocyte count indicates increased erythropoietic activity in the bone marrow, typically in response to anemia, blood loss, or hemolysis. Reticulocytes are immature red blood cells that still contain residual RNA and mature in the circulation within 1-2 days.

Question 29: Which preanalytical factor causes pseudohyperkalemia?

Fist clenching during venipuncture (Correct answer)
Short tourniquet application
Patient dehydration
Use of a serum separator tube

Correct answer: Fist clenching during venipuncture

Repeated fist clenching during venipuncture causes potassium release from forearm muscle cells, leading to pseudohyperkalemia. Patients should be instructed to keep their fist still during blood collection. Other causes include hemolysis and extreme leukocytosis or thrombocytosis.

Question 30: A laboratory receives a specimen for forensic toxicology testing. What is the most crucial documentation that must accompany the specimen from collection to analysis to ensure its legal admissibility?

A standard laboratory requisition form
A detailed patient clinical history
A signed patient consent form
A chain of custody form (Correct answer)

Correct answer: A chain of custody form

A chain of custody form provides a chronological and unbroken paper trail documenting the collection, handling, transfer, and storage of a specimen. For legal and forensic purposes, this documentation is essential to prove that the specimen was not tampered with, substituted, or altered at any point, ensuring its integrity and admissibility in court.

Question 31: Which parasitic infection is diagnosed by finding oval eggs with a lateral spine in urine specimens?

Enterobius vermicularis
Schistosoma mansoni
Trichomonas vaginalis
Schistosoma haematobium (Correct answer)

Correct answer: Schistosoma haematobium

Schistosoma haematobium eggs are found in urine and have a characteristic terminal spine. It is the only Schistosoma species that primarily affects the urinary tract, causing hematuria. S. mansoni eggs have a lateral spine and are found in stool. The question describes S. haematobium if the spine is terminal in urine specimens.

Question 32: What does the D-dimer test measure and what is its primary clinical application?

Fibrin degradation products from cross-linked fibrin; ruling out venous thromboembolism (Correct answer)
Fibrin monomer levels; diagnosing DIC
Factor V activity; monitoring warfarin
Platelet activation markers; diagnosing HIT

Correct answer: Fibrin degradation products from cross-linked fibrin; ruling out venous thromboembolism

D-dimer measures degradation products from cross-linked fibrin, indicating that both thrombin generation (clot formation) and plasmin activity (clot breakdown) have occurred. Its primary clinical use is ruling out deep vein thrombosis and pulmonary embolism due to its high negative predictive value.

Question 33: A pleural fluid analysis shows protein 45 g/L, LDH 500 U/L (serum LDH 200 U/L), glucose 2.0 mmol/L, and many lymphocytes. What diagnosis should be considered?

Uncomplicated pneumonia
Tuberculous pleuritis or malignancy (Correct answer)
Pulmonary embolism
Congestive heart failure

Correct answer: Tuberculous pleuritis or malignancy

This is an exudative effusion (high protein, LDH ratio >0.6) with lymphocyte predominance and low glucose. This pattern is characteristic of either tuberculous pleuritis or malignancy. Adenosine deaminase (ADA) levels >40 U/L support TB diagnosis. Cytology and pleural biopsy may be needed for malignancy diagnosis. AFB culture and NAAT for TB should be performed.

Question 34: Which staining technique is used to classify bacteria as gram-positive or gram-negative?

India ink stain
Gram stain (Correct answer)
Acid-fast stain
Giemsa stain

Correct answer: Gram stain

The Gram stain is the most fundamental staining technique in bacteriology. It differentiates bacteria based on cell wall composition: gram-positive bacteria (thick peptidoglycan layer) retain crystal violet and appear purple, while gram-negative bacteria (thin peptidoglycan, outer membrane) lose crystal violet during decolorization and stain pink with safranin.

Question 35: A Levey-Jennings chart for a quality control material shows that the last seven consecutive results have fallen above the mean. According to Westgard rules, this pattern is best described as a:

Calibration error
Trend
Random error
Shift (Correct answer)

Correct answer: Shift

A 'shift' is a quality control pattern where six or more consecutive data points fall on the same side of the mean. This indicates a sudden, systematic change in the test system. A trend would show a gradual increase or decrease, while a random error would show no discernible pattern.

Question 36: A stool culture yields a non-lactose fermenting, H2S-positive organism on Hektoen enteric agar. What is the most likely identification?

Shigella species
Yersinia enterocolitica
Escherichia coli
Salmonella species (Correct answer)

Correct answer: Salmonella species

On Hektoen enteric agar, Salmonella appears as blue-green colonies with black centers (H2S production). Salmonella does not ferment lactose or sucrose. Shigella appears similar but does not produce H2S. Further biochemical testing and serotyping are required for complete identification. Salmonella is reportable to public health.

Question 37: What is transfusion-related acute lung injury (TRALI)?

Fluid overload from too much blood
An allergic reaction causing asthma
A chronic lung condition from repeated transfusions
Acute respiratory distress occurring within 6 hours of transfusion, caused by donor antibodies activating recipient neutrophils in pulmonary capillaries (Correct answer)

Correct answer: Acute respiratory distress occurring within 6 hours of transfusion, caused by donor antibodies activating recipient neutrophils in pulmonary capillaries

TRALI is a serious complication characterized by acute bilateral pulmonary edema and hypoxia within 6 hours of transfusion, without other risk factors for acute lung injury. It is caused by donor anti-HLA or anti-HNA antibodies that activate recipient neutrophils in pulmonary capillaries. Risk reduction strategies include using male-only plasma donors.

Question 38: Which cell type is the precursor to platelets?

Reticulocyte
Myeloblast
Monoblast
Megakaryocyte (Correct answer)

Correct answer: Megakaryocyte

Megakaryocytes are the large bone marrow cells that produce platelets through cytoplasmic fragmentation. Each megakaryocyte can produce approximately 1,000-3,000 platelets. Thrombopoietin (TPO) is the primary growth factor regulating megakaryocyte development and platelet production.

Question 39: Which anatomical plane divides the body vertically into anterior and posterior (front and back) sections?

Coronal Plane (Correct answer)
Sagittal Plane
Transverse Plane
Oblique Plane

Correct answer: Coronal Plane

The coronal (or frontal) plane is a vertical plane that divides the body into anterior (front) and posterior (back) portions. The sagittal plane divides the body into left and right sides, and the transverse plane divides it into superior (upper) and inferior (lower) parts.

Question 40: A throat culture grows beta-hemolytic colonies. What additional testing should be performed?

Bacitracin susceptibility or PYR test to presumptively identify Group A Streptococcus (Correct answer)
Oxidase test
Coagulase test
Bile esculin test

Correct answer: Bacitracin susceptibility or PYR test to presumptively identify Group A Streptococcus

Beta-hemolytic colonies from throat culture should be tested with bacitracin (Group A Strep is susceptible, most other groups are resistant) or PYR test (Group A Strep is positive) for presumptive identification. Serological Lancefield grouping (latex agglutination) provides definitive group identification. Group A Strep is the primary throat pathogen requiring treatment.

Question 41: Which condition is characterized by elevated serum bilirubin with a predominantly unconjugated (indirect) fraction?

Hepatocellular carcinoma
Biliary obstruction
Cholestasis
Hemolytic anemia (Correct answer)

Correct answer: Hemolytic anemia

Hemolytic anemia causes elevated unconjugated (indirect) bilirubin because the excessive breakdown of red blood cells overwhelms the liver's capacity to conjugate bilirubin. In contrast, obstructive and hepatocellular conditions typically elevate conjugated (direct) bilirubin.

Question 42: Rheumatoid factor (RF) is typically an autoantibody of which immunoglobulin class directed against:

IgM directed against patient's own IgG (Correct answer)
IgA directed against collagen
IgG directed against nuclear antigens
IgE directed against IgM

Correct answer: IgM directed against patient's own IgG

Rheumatoid factor is classically an IgM autoantibody that targets the Fc region of the patient's own IgG, forming immune complexes that contribute to inflammation in rheumatoid arthritis.

Question 43: Which of the following best describes the purpose of the Medical Laboratory Technology Act in Ontario?

To establish laboratory accreditation standards for Ontario hospitals
To define the educational requirements for entry to MLT programs in Ontario colleges
To authorize the self-regulation of the medical laboratory technology profession and define its scope and controlled acts (Correct answer)
To set laboratory fee schedules under OHIP

Correct answer: To authorize the self-regulation of the medical laboratory technology profession and define its scope and controlled acts

The Medical Laboratory Technology Act (1991) is profession-specific legislation that establishes the CMLTO, defines the scope of practice, authorized controlled acts, and the framework for self-regulation of the MLT profession in Ontario.

Question 44: What does 'aliquoting' a specimen mean in laboratory specimen processing?

Discarding excess specimen after analysis
Filtering a specimen to remove particulates
Mixing a specimen by inversion before analysis
Dividing a primary specimen into smaller portions for multiple tests or storage (Correct answer)

Correct answer: Dividing a primary specimen into smaller portions for multiple tests or storage

Aliquoting involves transferring measured portions of a primary specimen into secondary tubes or containers to allow multiple tests to be performed from a single collection or for archival storage.

Question 45: What is the purpose of the Levey-Jennings chart in quality control?

To determine the analytical measurement range
To calculate reference ranges
To compare patient results between laboratories
To plot QC results over time and visually detect trends, shifts, and outliers (Correct answer)

Correct answer: To plot QC results over time and visually detect trends, shifts, and outliers

A Levey-Jennings chart plots QC values over time with the mean and standard deviation limits displayed. This visual tool allows laboratory professionals to identify patterns such as shifts (sudden change in mean), trends (gradual change), and outliers that indicate analytical problems.

Question 46: An MLT is asked by a colleague to process a stat sample for the colleague's own family member without a physician's requisition. What is the most appropriate response?

Process the sample with a retroactive requisition
Decline, as this violates professional and ethical standards (Correct answer)
Process the sample but flag it in the system
Process the sample as a professional courtesy

Correct answer: Decline, as this violates professional and ethical standards

Processing specimens without a valid physician's requisition violates laboratory policy, professional standards, and the ethical principle of maintaining professional boundaries.

Question 47: A D-negative pregnant woman at 28 weeks gestation has a negative antibody screen. What action should be taken?

Perform a Kleihauer-Betke test immediately
Administer antenatal Rh immune globulin (RhIg) at 28 weeks as prophylaxis (Correct answer)
No action needed
Induce labour early

Correct answer: Administer antenatal Rh immune globulin (RhIg) at 28 weeks as prophylaxis

Standard of care in Canada is to administer antenatal RhIg (300 µg IM) at 28 weeks gestation to D-negative women with negative antibody screens. This prevents sensitization from small fetomaternal hemorrhages that may occur during the third trimester. Additional RhIg is given postpartum within 72 hours if the baby is D-positive.

Question 48: The Transportation of Dangerous Goods Act requires packages that contain dry ice be shipped in:

a sealed container with a Miscellaneous Dangerous Goods label.
an unsealed container with absorbent material and a Dangerous Goods label.
an unsealed container with a Miscellaneous Dangerous Goods label. (Correct answer)
a sealed container with absorbent material and a Dangerous Goods label.
a sealed container with a Dangerous Goods label only.

Correct answer: an unsealed container with a Miscellaneous Dangerous Goods label.

For a minor spill of radioactive material, the primary procedures involve containing the package, following standard decontamination, and placing it in a shielded area. Notifying local authorities (like police or fire departments) is typically reserved for major spills that pose a significant public health risk, not for minor, contained leaks that can be managed internally with established protocols.

Question 49: Which coagulation factor is deficient in hemophilia A?

Factor XI
Factor IX
Factor VIII (Correct answer)
Factor VII

Correct answer: Factor VIII

Hemophilia A is caused by deficiency of Factor VIII, an essential cofactor in the intrinsic pathway. It is an X-linked recessive disorder primarily affecting males. Severity depends on residual Factor VIII activity: severe (<1%), moderate (1-5%), or mild (5-40%).

Question 50: The administration of CPR on an adult requires how many chest compressions performed immediately before a series of two breaths is given?

25
0
20
30 (Correct answer)
5

Correct answer: 30

According to current CPR guidelines for adults, the recommended ratio of chest compressions to breaths is 30 compressions followed by 2 breaths. This sequence should be repeated until emergency medical services arrive or the person shows signs of recovery. Maintaining a compression rate of 100-120 compressions per minute is also crucial for effective CPR.

Question 51: Which blood group system is most commonly associated with hemolytic disease of the fetus and newborn (HDFN)?

ABO system
Duffy system
Kell system
Rh system (specifically anti-D) (Correct answer)

Correct answer: Rh system (specifically anti-D)

While ABO HDFN is most common, Rh (anti-D) HDFN is the most clinically severe form. An Rh-negative mother carrying an Rh-positive fetus can develop anti-D, which crosses the placenta and destroys fetal red cells. RhIg (WinRho/Rhogam) prophylaxis at 28 weeks and after delivery has dramatically reduced anti-D HDFN.

Question 52: What type of quality control chart is used to monitor the mean and variation of laboratory analytical results over time?

Run chart only
Pareto chart
Scatter plot
Levey-Jennings chart (Correct answer)

Correct answer: Levey-Jennings chart

The Levey-Jennings chart plots QC results over time against mean and ±1, ±2, and ±3 SD control limits, allowing visual detection of shifts, trends, and random error in laboratory analytical performance.

Question 53: Which of the following items is NOT found in cryoprecipitate?

Factor XII
Fibrinogen
Factor V (Correct answer)
Factor VIII
Factor 1

Correct answer: Factor V

Cryoprecipitate is a concentrated plasma derivative rich in specific clotting factors that precipitate out when fresh frozen plasma is thawed at cold temperatures. It primarily contains Factor I (fibrinogen), Factor VIII, Factor XIII, and von Willebrand factor. Factor V, however, remains in the cryoprecipitate-poor plasma and is therefore not found in significant amounts in cryoprecipitate.

Question 54: A patient's hemoglobin is 145 g/L and hematocrit (Hct) is 0.44 L/L. Calculate the Mean Corpuscular Hemoglobin Concentration (MCHC) using the formula: MCHC = Hgb (g/L) ÷ Hct (L/L).

300.0 g/L
329.5 g/L (Correct answer)
63.8 g/L
145.0 g/L

Correct answer: 329.5 g/L

MCHC = Hgb ÷ Hct = 145 ÷ 0.44 = 329.5 g/L.

Question 55: What does the mean corpuscular volume (MCV) measure?

The variation in red blood cell size
The average size (volume) of red blood cells (Correct answer)
The average hemoglobin content per red blood cell
The average hemoglobin concentration within red blood cells

Correct answer: The average size (volume) of red blood cells

MCV measures the average volume of individual red blood cells in femtoliters (fL). The normal range is approximately 80-100 fL. Low MCV (microcytic) suggests iron deficiency or thalassemia, while high MCV (macrocytic) suggests vitamin B12/folate deficiency or liver disease.

Question 56: What is the significance of finding oval fat bodies in urine?

They indicate nephrotic syndrome with lipiduria (Correct answer)
Normal finding in concentrated urine
They are caused by contamination
They indicate urinary tract infection

Correct answer: They indicate nephrotic syndrome with lipiduria

Oval fat bodies are renal tubular epithelial cells or macrophages that have absorbed lipid (cholesterol and triglycerides). They are highly characteristic of nephrotic syndrome, where massive proteinuria is accompanied by hyperlipidemia and lipiduria. Under polarized light, cholesterol in oval fat bodies shows a characteristic Maltese cross pattern.

Question 57: A patient has hemoglobin 70 g/L, MCV 110 fL, hypersegmented neutrophils, and elevated methylmalonic acid. What is the most likely diagnosis?

Myelodysplastic syndrome
Liver disease
Vitamin B12 deficiency (Correct answer)
Folate deficiency

Correct answer: Vitamin B12 deficiency

Macrocytic anemia with hypersegmented neutrophils indicates megaloblastic anemia. The elevated methylmalonic acid (MMA) specifically distinguishes vitamin B12 deficiency from folate deficiency, as MMA requires B12-dependent methylmalonyl-CoA mutase. MMA is normal in folate deficiency but elevated in B12 deficiency.

Question 58: A blood bank receives two patient specimens with the same name but different dates of birth. How should this discrepancy be handled?

Use whichever specimen was collected first
Do not process either specimen for transfusion until the patient identity discrepancy is resolved and a new properly identified specimen is collected (Correct answer)
Process both specimens normally
Process based on blood type match

Correct answer: Do not process either specimen for transfusion until the patient identity discrepancy is resolved and a new properly identified specimen is collected

Any discrepancy in patient identification is a critical safety issue. Neither specimen should be processed until the identity confusion is resolved. A new specimen must be collected with proper bedside identification. Wrong patient identification is the leading cause of fatal ABO-incompatible transfusions. Never make assumptions about patient identity.

Question 59: Which specimen processing step is critical for recovery of Mycobacterium tuberculosis from sputum?

Direct inoculation onto blood agar
Digestion and decontamination with NALC-NaOH (Correct answer)
Filtration through a 0.22 µm membrane
Enrichment in thioglycollate broth

Correct answer: Digestion and decontamination with NALC-NaOH

Sputum specimens for mycobacterial culture require digestion and decontamination with N-acetyl-L-cysteine (NALC) as a mucolytic agent and sodium hydroxide (NaOH) to kill contaminating bacteria. This step is critical because mycobacteria grow slowly (2-8 weeks) and would be overgrown by faster-growing normal flora.

Question 60: A technologist needs to dilute a patient sample that has a potassium result of 9.2 mmol/L (above linearity). After a 1:2 dilution with saline, the re-measured result is 4.8 mmol/L. What is the corrected patient potassium?

9.6 mmol/L (Correct answer)
2.4 mmol/L
4.8 mmol/L
7.2 mmol/L

Correct answer: 9.6 mmol/L

Multiply the diluted result by the dilution factor: 4.8 × 2 = 9.6 mmol/L.

Question 61: What investigation must be performed when a transfusion reaction is suspected?

No investigation needed if symptoms resolve
Continue transfusion at a slower rate
Stop transfusion, clerical check, visual inspection of post-transfusion sample for hemolysis, DAT, repeat ABO/Rh on pre- and post-transfusion samples (Correct answer)
Only check the patient's temperature

Correct answer: Stop transfusion, clerical check, visual inspection of post-transfusion sample for hemolysis, DAT, repeat ABO/Rh on pre- and post-transfusion samples

Transfusion reaction investigation includes: 1) Stop the transfusion immediately, 2) Clerical verification of patient and unit identification, 3) Visual inspection for hemolysis (pink/red serum), 4) DAT on post-transfusion sample, 5) Repeat ABO/Rh typing on pre- and post-transfusion samples, 6) Notify blood bank. Additional tests may include urinalysis, bilirubin, haptoglobin, and LDH.

Question 62: A patient with a mechanical heart valve has an INR target of 2.5-3.5. Their current INR is 2.0. What action should be taken?

Increase the warfarin dose slightly to achieve the higher target range (Correct answer)
Add aspirin instead of adjusting warfarin
Discontinue warfarin
No change needed, this is within range

Correct answer: Increase the warfarin dose slightly to achieve the higher target range

Patients with mechanical heart valves require higher INR targets (typically 2.5-3.5 depending on valve position and type) compared to patients with atrial fibrillation or venous thromboembolism (target 2.0-3.0). An INR of 2.0 is below the therapeutic range and requires a modest dose increase.

Question 63: Which coagulation test measures the extrinsic and common pathways?

Thrombin time (TT)
Prothrombin time (PT) (Correct answer)
Fibrinogen assay
Activated partial thromboplastin time (aPTT)

Correct answer: Prothrombin time (PT)

The prothrombin time (PT) measures the extrinsic (Factor VII) and common (Factors X, V, II, and fibrinogen) coagulation pathways. It is triggered by adding tissue thromboplastin (tissue factor) and calcium to citrated plasma. PT/INR is used to monitor warfarin therapy.

Question 64: A blood specimen collected in a plain red-top tube at 9:00 AM must be centrifuged within 30 minutes of collection. What is the latest acceptable centrifugation time?

9:30 AM (Correct answer)
10:00 AM
9:15 AM
9:45 AM

Correct answer: 9:30 AM

Adding 30 minutes to the 9:00 AM collection time gives 9:30 AM as the deadline for centrifugation.

Question 65: When performing venipuncture, the tourniquet should be removed from the patient's arm at what point?

Before inserting the needle to prevent hemoconcentration
After the last tube has been filled and before needle removal (Correct answer)
Immediately after needle insertion
Only after applying pressure to the site

Correct answer: After the last tube has been filled and before needle removal

The tourniquet should be released after the last tube is filled and before the needle is withdrawn to prevent hematoma formation and restore normal circulation.

Question 66: Which organism is the most common cause of community-acquired urinary tract infections?

Pseudomonas aeruginosa
Staphylococcus aureus
Escherichia coli (Correct answer)
Enterococcus faecalis

Correct answer: Escherichia coli

Escherichia coli is responsible for approximately 75-90% of uncomplicated community-acquired urinary tract infections. E. coli possesses virulence factors including type 1 pili and P fimbriae that facilitate adherence to uroepithelial cells. Other common uropathogens include Klebsiella, Proteus, and Staphylococcus saprophyticus.

Question 67: Which serological test is used for the diagnosis of syphilis and what is the screening algorithm used in Canada?

RPR only; no confirmation needed
Dark-field microscopy for all stages
FTA-ABS as the sole test
Reverse algorithm: treponemal test (EIA/CIA) screen followed by RPR and confirmatory treponemal test (Correct answer)

Correct answer: Reverse algorithm: treponemal test (EIA/CIA) screen followed by RPR and confirmatory treponemal test

Many Canadian laboratories use the reverse syphilis screening algorithm: a treponemal-specific immunoassay (EIA or CIA) is used for screening, followed by RPR (a non-treponemal test to assess disease activity) and a second treponemal test (TP-PA or FTA-ABS) for confirmation. This approach has higher sensitivity for detecting latent syphilis.

Question 68: What is the mucin clot test (Ropes test) used for in synovial fluid analysis?

Testing for bacterial infection
Measuring glucose levels
Assessing the quality of hyaluronic acid in synovial fluid; a poor clot suggests inflammatory degradation of hyaluronic acid (Correct answer)
Detecting crystals

Correct answer: Assessing the quality of hyaluronic acid in synovial fluid; a poor clot suggests inflammatory degradation of hyaluronic acid

The mucin clot test assesses hyaluronic acid integrity by adding acetic acid to synovial fluid. Normal synovial fluid forms a firm, cohesive clot (good mucin clot). Inflammatory conditions (rheumatoid arthritis, septic arthritis) degrade hyaluronic acid through enzymatic action, producing a poor or friable clot. This test has largely been replaced by more specific analyses.

Question 69: A patient taking unfractionated heparin develops a platelet drop from 250 to 100 × 10⁹/L on day 7 with a new DVT. The 4T score is 7. What is the next step?

Switch to low-molecular-weight heparin
Immediately stop all heparin, start alternative anticoagulant, and send HIT antibody testing (Correct answer)
Transfuse platelets
Continue heparin and monitor

Correct answer: Immediately stop all heparin, start alternative anticoagulant, and send HIT antibody testing

A high 4T score (6-8) with >50% platelet drop, timing on day 7, and new thrombosis strongly suggests HIT type II. All heparin must be stopped immediately (including flushes), an alternative non-heparin anticoagulant started (argatroban or fondaparinux), and HIT antibody testing sent. LMWH cross-reacts with HIT antibodies and is contraindicated.

Question 70: Which anticoagulant is used in tubes for the complete blood count (CBC)?

Lithium heparin
EDTA (ethylenediaminetetraacetic acid) (Correct answer)
Sodium fluoride
Sodium citrate

Correct answer: EDTA (ethylenediaminetetraacetic acid)

EDTA (lavender-top tube) is the anticoagulant of choice for CBC testing because it preserves cell morphology and prevents platelet clumping. EDTA chelates calcium ions, preventing coagulation while maintaining cellular integrity for accurate automated and manual cell counting.

Question 71: A technologist performs a serial dilution starting with a 1:2 dilution, followed by three additional 1:2 dilutions. What is the final dilution factor of the last tube?

1:32
1:16 (Correct answer)
1:10
1:8

Correct answer: 1:16

Each 1:2 dilution doubles the dilution factor. After 4 sequential 1:2 dilutions: 2¹ × 2¹ × 2¹ × 2¹ = 2⁴ = 1:16.

Question 72: A patient with diabetes has a urine showing 2+ glucose, 2+ ketones, specific gravity 1.035, and pH 5.0. What is the clinical correlation?

Well-controlled diabetes
Normal diabetic monitoring
Diabetic ketoacidosis (DKA) or poor glycemic control — glucosuria with ketonuria in concentrated, acidic urine (Correct answer)
Urinary tract infection

Correct answer: Diabetic ketoacidosis (DKA) or poor glycemic control — glucosuria with ketonuria in concentrated, acidic urine

Glucosuria (blood glucose exceeds renal threshold) with ketonuria (increased fat metabolism due to insulin deficiency) in concentrated, acidic urine suggests poor glycemic control or impending/active diabetic ketoacidosis. The high specific gravity indicates dehydration (common in DKA due to osmotic diuresis). Blood glucose and blood gas analysis should be performed urgently.

Question 73: An experienced MLA/T observes a newly certified colleague failing to follow the established quality control procedure for a point-of-care testing device. According to the MLPAO and CSMLS Codes of Ethics, what is the most appropriate initial action?

Ignore the deviation as the colleague is new and will learn from their mistakes.
Report the colleague to the laboratory supervisor immediately.
Document the error in the colleague's personnel file.
Privately and respectfully remind the colleague of the correct procedure. (Correct answer)

Correct answer: Privately and respectfully remind the colleague of the correct procedure.

Professional codes of ethics emphasize responsibility, collegiality, and patient safety. The most appropriate initial step is to address the issue directly and constructively with the colleague. This provides an opportunity for immediate correction, mentorship, and reinforcement of quality standards without immediately escalating the issue, assuming it was an unintentional error.

Question 74: Which liver enzyme is most specific for biliary obstruction?

Alanine aminotransferase (ALT)
5'-Nucleotidase (Correct answer)
Gamma-glutamyltransferase (GGT)
Aspartate aminotransferase (AST)

Correct answer: 5'-Nucleotidase

5'-Nucleotidase is the most specific enzyme for biliary obstruction because it is primarily found in hepatobiliary tissue. While alkaline phosphatase and GGT are also elevated in cholestasis, they can be elevated in bone disease and other conditions respectively.

Question 75: A urine sample from a patient on the antibiotic nitrofurantoin shows a brown/dark colour. The dipstick is negative for blood. What explains the colour?

Drug-induced colour change — nitrofurantoin metabolites produce brown/rust-coloured urine as a known harmless side effect (Correct answer)
Myoglobinuria
Bilirubinuria
Hematuria

Correct answer: Drug-induced colour change — nitrofurantoin metabolites produce brown/rust-coloured urine as a known harmless side effect

Several medications cause distinctive urine colour changes: nitrofurantoin (brown/rust), rifampin (red-orange), phenazopyridine (bright orange), and metronidazole (dark/red-brown). These are harmless metabolite effects. The negative blood dipstick rules out hematuria. Patient medication history is essential when investigating abnormal urine colour.

Question 76: What does the coefficient of variation (CV%) measure in laboratory analytical performance?

The systematic bias between the laboratory and a reference method
The acceptable range of analyte values in a healthy population
The difference between the highest and lowest QC values
The degree of random variation in a method expressed as a percentage of the mean (Correct answer)

Correct answer: The degree of random variation in a method expressed as a percentage of the mean

The CV% (coefficient of variation) expresses imprecision (random variation) as a percentage of the mean: CV% = (SD/Mean) × 100. Lower CV% indicates better precision.

Question 77: What is the appropriate response when a laboratory identifies Neisseria meningitidis from a clinical specimen?

Immediately notify the physician and public health for contact prophylaxis (Correct answer)
Report routine results only
Wait for susceptibility results before reporting
Report only if from CSF

Correct answer: Immediately notify the physician and public health for contact prophylaxis

N. meningitidis isolation from any normally sterile site (blood, CSF) requires immediate physician notification and public health reporting. Close contacts need chemoprophylaxis (rifampin, ciprofloxacin, or ceftriaxone) within 24 hours to prevent secondary cases. This is a reportable disease in all Canadian jurisdictions.

Question 78: What is the universal red blood cell donor type and why?

Type B negative
Type AB positive
Type A positive
Type O negative, because O red cells lack A and B antigens and D antigen (Correct answer)

Correct answer: Type O negative, because O red cells lack A and B antigens and D antigen

Type O negative is the universal red blood cell donor because the red cells lack A, B, and D antigens, minimizing the risk of ABO and Rh-related transfusion reactions. O negative blood is used in emergency situations when there is no time for typing. However, it is a limited resource (about 7% of the Canadian population).

Question 79: Which organism is the most common cause of bacterial meningitis in Canadian adults?

Listeria monocytogenes
Haemophilus influenzae type b
Streptococcus pneumoniae (Correct answer)
Escherichia coli

Correct answer: Streptococcus pneumoniae

Streptococcus pneumoniae is the most common cause of bacterial meningitis in adults in Canada. It appears as gram-positive lancet-shaped diplococci on CSF Gram stain. Since the introduction of Hib vaccine, H. influenzae meningitis has decreased dramatically. In neonates, Group B Streptococcus and E. coli are more common.

Question 80: Which specimen type is preferred for most clinical chemistry analyses?

Plasma from a heparin tube
Serum from a red-top tube (Correct answer)
Whole blood in EDTA
Capillary blood

Correct answer: Serum from a red-top tube

Serum collected in a red-top (no additive) tube or serum separator tube (SST) is preferred for most clinical chemistry analyses. Serum lacks fibrinogen and clotting factors, providing a cleaner matrix that minimizes interference with many analytical methods.

Question 81: Which analyte is most affected by improper specimen transport temperature?

Total protein
Ammonia (Correct answer)
Sodium
Chloride

Correct answer: Ammonia

Ammonia is extremely sensitive to transport conditions. Specimens must be placed on ice immediately after collection and analyzed within 15-30 minutes. At room temperature, deamination of amino acids and other nitrogen-containing compounds causes rapid ammonia generation, leading to falsely elevated results.

Question 82: A patient on warfarin has an INR of 8.5 with no active bleeding. What is the recommended management?

Increase warfarin dose
Hold warfarin and administer oral vitamin K (Correct answer)
Give fresh frozen plasma immediately
Continue warfarin at the same dose

Correct answer: Hold warfarin and administer oral vitamin K

For an INR >4.5-10 without significant bleeding, the recommended approach is to hold warfarin and administer low-dose oral vitamin K (1-2.5 mg). This will lower the INR within 24-48 hours. Fresh frozen plasma or prothrombin complex concentrate is reserved for active life-threatening bleeding.

Question 83: A urine dipstick shows 3+ blood but microscopic examination reveals no red blood cells. What is the most likely explanation?

Hemoglobinuria or myoglobinuria — free hemoglobin or myoglobin in urine causes a positive dipstick without intact RBCs (Correct answer)
The microscopy was performed incorrectly
The dipstick is expired
False positive dipstick

Correct answer: Hemoglobinuria or myoglobinuria — free hemoglobin or myoglobin in urine causes a positive dipstick without intact RBCs

A positive blood dipstick without microscopic RBCs indicates hemoglobinuria (from intravascular hemolysis) or myoglobinuria (from rhabdomyolysis). Both hemoglobin and myoglobin contain heme groups that catalyze the dipstick peroxidase reaction. Serum examination (pink/red = hemolysis; clear = myoglobinuria) and CK levels help differentiate.

Question 84: A laboratory identifies a Salmonella species from a stool culture. What is the reporting obligation in Canada?

No reporting is required
Only typhoid Salmonella needs reporting
Reporting is optional and at the physician's discretion
Salmonella is a reportable/notifiable disease and must be reported to public health authorities (Correct answer)

Correct answer: Salmonella is a reportable/notifiable disease and must be reported to public health authorities

Salmonellosis is a reportable/notifiable disease in all Canadian provinces and territories. The laboratory must report the isolation to local public health authorities. Isolates may be sent to a reference laboratory for serotyping and molecular typing for outbreak investigation and surveillance purposes.

Question 85: What is autoabsorption and when is it used in the blood bank?

Absorbing all antibodies from serum
Adding antibiotics to remove bacterial contamination
Testing patient cells for autoantigens
Removing autoantibodies from patient serum using the patient's own red cells to unmask underlying alloantibodies (Correct answer)

Correct answer: Removing autoantibodies from patient serum using the patient's own red cells to unmask underlying alloantibodies

Autoabsorption is performed when a patient has warm autoantibodies (warm autoimmune hemolytic anemia) that react with all panel cells, making it impossible to detect underlying alloantibodies. Patient's own red cells (treated with enzymes to enhance adsorption) are incubated with the serum to remove autoantibody, and the absorbed serum is tested for alloantibodies.

Question 86: What does the urine specific gravity measure?

The concentration of dissolved solutes in urine relative to water (Correct answer)
Urine pH
Urine volume
The number of cells in urine

Correct answer: The concentration of dissolved solutes in urine relative to water

Specific gravity measures the density of urine compared to pure water (1.000), reflecting the kidney's ability to concentrate or dilute urine. Normal range is 1.005-1.030. High specific gravity (>1.030) indicates concentrated urine (dehydration), while low specific gravity (1.001-1.005) indicates dilute urine. Fixed specific gravity (1.010) suggests renal tubular dysfunction.

Question 87: In clinical chemistry, what is the difference between an 'endpoint' and a 'kinetic' (rate) assay?

Endpoint assays detect enzymes; kinetic assays detect substrates
Endpoint assays use whole blood; kinetic assays require serum
Endpoint assays measure absorbance after the reaction is complete; kinetic assays measure the rate of absorbance change during the reaction (Correct answer)
Endpoint assays are faster; kinetic assays are more accurate

Correct answer: Endpoint assays measure absorbance after the reaction is complete; kinetic assays measure the rate of absorbance change during the reaction

Endpoint assays measure absorbance after the reaction has gone to completion; kinetic assays measure the rate of absorbance change per minute during the reaction, which is proportional to enzyme activity or analyte concentration.

Question 88: What is the trichrome stain used for in parasitology?

Staining malaria parasites in blood
Detecting acid-fast organisms
Identifying fungal hyphae
Permanent staining of intestinal protozoan trophozoites and cysts in stool specimens (Correct answer)

Correct answer: Permanent staining of intestinal protozoan trophozoites and cysts in stool specimens

The trichrome stain is a permanent stain for identifying intestinal protozoa (such as Entamoeba histolytica, Giardia lamblia, and Dientamoeba fragilis) in stool specimens preserved in polyvinyl alcohol (PVA) or SAF fixative. It provides excellent detail of nuclear and cytoplasmic features essential for accurate species identification.

Question 89: A reagent requires a 1 in 50 dilution (1:50) to prepare a working solution. If you need 200 mL of working solution, how many mL of reagent concentrate do you need?

50 mL
2 mL
10 mL
4 mL (Correct answer)

Correct answer: 4 mL

Volume of concentrate = Final volume ÷ Dilution factor = 200 ÷ 50 = 4 mL.

Question 90: For a glucose tolerance test (GTT), a 75g oral glucose challenge is administered. When is the post-load blood specimen collected for a standard 2-hour OGTT?

60 minutes after glucose ingestion
120 minutes (2 hours) after glucose ingestion (Correct answer)
90 minutes after glucose ingestion
30 minutes after glucose ingestion

Correct answer: 120 minutes (2 hours) after glucose ingestion

The standard 2-hour OGTT (oral glucose tolerance test) requires collection of a blood specimen exactly 120 minutes (2 hours) after the patient finishes drinking the 75g glucose solution.

Question 91: What is the principle of the thrombin time (TT) test?

Measures the time for plasma to clot after adding tissue factor
Measures the time for plasma to clot after adding thrombin directly (Correct answer)
Measures the activity of Factor VIII
Measures platelet adhesion to collagen

Correct answer: Measures the time for plasma to clot after adding thrombin directly

The thrombin time measures the time for fibrin clot formation after adding exogenous thrombin directly to citrated plasma, bypassing the intrinsic and extrinsic pathways. It evaluates the final step of coagulation (fibrinogen to fibrin conversion) and is prolonged by heparin, low fibrinogen, dysfibrinogenemia, and elevated FDPs.

Question 92: Which condition is associated with basophilic stippling of red blood cells?

Hereditary spherocytosis
Iron deficiency anemia
Paroxysmal nocturnal hemoglobinuria
Lead poisoning and thalassemia (Correct answer)

Correct answer: Lead poisoning and thalassemia

Basophilic stippling (blue granules in red blood cells representing aggregated ribosomes) is characteristically seen in lead poisoning (lead inhibits pyrimidine 5'-nucleotidase) and thalassemia. It can also be seen in sideroblastic anemia, heavy metal poisoning, and myelodysplastic syndromes.

Question 93: An MLA is tasked with preparing aliquots from a primary plasma sample for multiple downstream tests. Which of the following is the MOST critical step to perform immediately before pipetting the plasma into the secondary tubes?

Check the primary sample for fibrin clots.
Ensure the aliquot tubes are pre-chilled.
Gently mix the primary sample by inversion. (Correct answer)
Verify the patient's fasting status.

Correct answer: Gently mix the primary sample by inversion.

After centrifugation and potential storage, concentration gradients of analytes can form within the plasma or serum. Gently mixing the primary sample by inversion before aliquoting ensures that each aliquot is a homogenous and representative portion of the original specimen, which is crucial for accurate and consistent test results.

Question 94: A patient has hemoglobin 85 g/L, MCV 65 fL, RDW 18%, and serum ferritin 5 µg/L. What is the most likely diagnosis?

Iron deficiency anemia (Correct answer)
Sideroblastic anemia
Beta-thalassemia trait
Anemia of chronic disease

Correct answer: Iron deficiency anemia

The combination of low hemoglobin, microcytosis (MCV 65 fL), elevated RDW (anisocytosis), and very low ferritin (5 µg/L) is classic for iron deficiency anemia. Beta-thalassemia trait typically has a normal RDW and normal ferritin. The low ferritin is the most specific finding for iron deficiency.

Question 95: What is the electronic (computer) crossmatch and when can it be used?

A virtual crossmatch using genetic data
An automated serological crossmatch
A crossmatch performed using electronic microscopy
A computer-verified ABO compatibility check between patient and donor, used when the antibody screen is negative and the patient has no history of clinically significant antibodies (Correct answer)

Correct answer: A computer-verified ABO compatibility check between patient and donor, used when the antibody screen is negative and the patient has no history of clinically significant antibodies

The electronic crossmatch uses the laboratory information system to verify ABO compatibility between the patient and donor unit without serological testing. It requires: 1) Two concordant ABO/Rh typings on the patient, 2) Negative current antibody screen, 3) No history of clinically significant antibodies, 4) Validated computer system. It improves blood availability and reduces testing time.

Question 96: What is the significance of the Duffy blood group system in relation to malaria?

Duffy antigens have no relation to malaria
Duffy antigens cause malaria
The Duffy antigen Fy(a)/Fy(b) serves as the receptor for Plasmodium vivax; Duffy-negative individuals are resistant to P. vivax malaria (Correct answer)
Duffy antigens protect against P. falciparum

Correct answer: The Duffy antigen Fy(a)/Fy(b) serves as the receptor for Plasmodium vivax; Duffy-negative individuals are resistant to P. vivax malaria

The Duffy glycoprotein (DARC) serves as the receptor for P. vivax merozoite invasion of red blood cells. The Fy(a-b-) phenotype (common in individuals of West African descent due to a GATA-1 binding site mutation) confers resistance to P. vivax malaria. This selective advantage has maintained the high frequency of the Duffy-null phenotype in malaria-endemic regions.

Question 97: A patient requests access to their own laboratory test results. Under the Personal Health Information Protection Act (PHIPA) in Ontario, what is the laboratory's obligation?

Provide access within 30 days with limited exceptions (Correct answer)
Refuse, as results must go through the ordering physician only
Provide access only if the physician provides written consent
Direct the patient to the hospital records department exclusively

Correct answer: Provide access within 30 days with limited exceptions

PHIPA grants patients the right to access their own personal health information within 30 days of a request, with limited exceptions such as risk of serious harm.

Question 98: For which of the following specimens is maintaining sterility during collection of utmost importance to ensure accurate results?

24-hour urine for creatinine clearance
Blood specimen for a lipid panel
Random urine for routine urinalysis
Urine for culture and sensitivity (Correct answer)

Correct answer: Urine for culture and sensitivity

When collecting a urine specimen for culture and sensitivity, the goal is to identify and quantify bacteria from a potential urinary tract infection. Contamination of the specimen with bacteria from the skin or surrounding environment can lead to false-positive results and inappropriate antibiotic treatment. Therefore, a sterile container and a 'mid-stream clean catch' technique are essential.

Question 99: What is the significance of extended incubation (up to 14 days) for blood cultures from patients with suspected endocarditis?

Extended incubation is never needed with modern systems
Extended incubation only detects contaminants
Extended incubation is for fungal detection only
Some endocarditis pathogens (HACEK group, Brucella) are slow-growing and may not be detected in standard 5-day incubation (Correct answer)

Correct answer: Some endocarditis pathogens (HACEK group, Brucella) are slow-growing and may not be detected in standard 5-day incubation

HACEK organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella) and other fastidious endocarditis pathogens may require extended incubation (up to 14 days) for detection. Modern automated systems detect most pathogens within 5 days, but the microbiology laboratory should be notified of suspected endocarditis to ensure appropriate incubation.

Question 100: An MLA performs a gravimetric check on a P1000 micropipette set to dispense 1000 µL. The average mass of ten dispenses of reagent water is 0.982 g, which converts to a volume of 982 µL. This finding indicates a primary problem with the pipette's:

Precision
Ergonomics
Accuracy (Correct answer)
Tip compatibility

Correct answer: Accuracy

Accuracy is the measure of how close a dispensed volume is to the intended or set volume. Since the average volume (982 µL) is significantly different from the target volume (1000 µL), the pipette is inaccurate. Precision refers to the repeatability or closeness of the ten individual measurements to each other, which cannot be determined from the average alone.

Question 101: A post-transfusion DAT is positive with anti-IgG but negative with anti-C3d. The eluate contains anti-c. What type of reaction is this?

Febrile non-hemolytic transfusion reaction
Delayed hemolytic transfusion reaction due to an anamnestic anti-c response (Correct answer)
Bacterial contamination
Autoimmune hemolytic anemia

Correct answer: Delayed hemolytic transfusion reaction due to an anamnestic anti-c response

A positive post-transfusion DAT with anti-IgG and an eluate showing anti-c indicates a delayed hemolytic transfusion reaction. The patient was previously sensitized to the c antigen, and anti-c was undetectable at the time of the pre-transfusion antibody screen. Re-exposure to c-positive donor cells triggered an anamnestic response, producing anti-c that now coats the transfused cells.

Question 102: Which laboratory test is used to monitor direct oral anticoagulants (DOACs) when needed?

aPTT for all DOACs
Fibrinogen assay
PT/INR for all DOACs
Anti-Xa assay for rivaroxaban/apixaban; dilute thrombin time for dabigatran (Correct answer)

Correct answer: Anti-Xa assay for rivaroxaban/apixaban; dilute thrombin time for dabigatran

When DOAC levels need to be measured (emergency surgery, overdose, renal impairment), drug-specific calibrated assays are used. Anti-Xa assays calibrated with the specific drug measure rivaroxaban and apixaban levels. Dilute thrombin time or ecarin clotting time measures dabigatran levels.

Question 103: Which enzyme is measured to confirm the hepatic origin of an elevated alkaline phosphatase?

Amylase
Alanine aminotransferase (ALT)
Gamma-glutamyltransferase (GGT) (Correct answer)
Creatine kinase (CK)

Correct answer: Gamma-glutamyltransferase (GGT)

GGT is used to confirm the hepatic origin of an elevated alkaline phosphatase. If both ALP and GGT are elevated, the ALP is likely of hepatobiliary origin. If ALP is elevated but GGT is normal, the ALP elevation is likely from bone or other non-hepatic sources.

Question 104: What causes a delta check failure in the clinical chemistry laboratory?

A QC result exceeding 2 standard deviations
A significant difference between a patient's current and previous result (Correct answer)
A reagent lot change
An instrument calibration failure

Correct answer: A significant difference between a patient's current and previous result

A delta check compares a patient's current test result with their previous result and flags significant changes that may indicate specimen misidentification, sample mix-up, or acute clinical change. The acceptable delta varies by analyte and is typically expressed as a percentage or absolute change.

Question 105: A 70-year-old patient has WBC 85 × 10⁹/L with 90% mature lymphocytes and numerous smudge cells. What is the most likely diagnosis?

Acute lymphoblastic leukemia
Chronic lymphocytic leukemia (Correct answer)
Chronic myeloid leukemia
Infectious mononucleosis

Correct answer: Chronic lymphocytic leukemia

The clinical picture of an elderly patient with markedly elevated WBC, predominance of mature lymphocytes, and smudge cells (basket cells) is classic for chronic lymphocytic leukemia (CLL). Smudge cells result from the fragility of CLL lymphocytes during smear preparation. Immunophenotyping would show CD5+, CD19+, CD23+ B cells.

Question 106: An MLA/T is tasked with collecting blood for coagulation studies (light blue top), a complete blood count (lavender top), and a basic metabolic panel (serum separator tube - SST). To prevent additive cross-contamination, what is the correct order of draw?

Light blue top, SST, Lavender top (Correct answer)
Lavender top, SST, Light blue top
Light blue top, Lavender top, SST
SST, Lavender top, Light blue top

Correct answer: Light blue top, SST, Lavender top

The correct order of draw is based on CLSI guidelines to prevent contamination of specimens by additives from other tubes. The sequence is: 1) Blood cultures, 2) Sodium Citrate (light blue top) for coagulation, 3) Serum tubes with or without clot activator/gel (SST), 4) Heparin (green top), 5) EDTA (lavender top), and 6) Glycolytic inhibitor (gray top). Following this order ensures that the citrate tube for coagulation is drawn before tubes with clot activators or other additives that could interfere with testing.

Question 107: What is the primary purpose of a laboratory's standard operating procedure (SOP)?

To provide a reference for patient result interpretation
To satisfy accreditation requirements only
To ensure consistent, reproducible performance of procedures by all staff (Correct answer)
To document equipment maintenance schedules

Correct answer: To ensure consistent, reproducible performance of procedures by all staff

SOPs ensure that all laboratory staff perform procedures in a standardized, consistent, and reproducible manner, which is essential for result accuracy and patient safety.

Question 108: A Gram stain of a positive blood culture shows gram-positive cocci in clusters. What organism is most likely and what empiric therapy should be communicated?

Streptococcus pneumoniae; penicillin
Neisseria meningitidis; ceftriaxone
Staphylococcus species; vancomycin pending identification and susceptibilities (Correct answer)
Enterococcus; ampicillin

Correct answer: Staphylococcus species; vancomycin pending identification and susceptibilities

Gram-positive cocci in clusters from blood culture is most consistent with Staphylococcus species. Because MRSA must be considered, empiric vancomycin is recommended until species identification and susceptibility results are available. If methicillin-susceptible S. aureus (MSSA) is confirmed, therapy is narrowed to cloxacillin/cefazolin.

Question 109: Which molecular test is used for rapid detection of Mycobacterium tuberculosis and rifampin resistance?

Interferon-gamma release assay
AFB culture on Lowenstein-Jensen medium
GeneXpert MTB/RIF (Xpert) (Correct answer)
Mantoux tuberculin skin test

Correct answer: GeneXpert MTB/RIF (Xpert)

GeneXpert MTB/RIF is a rapid, cartridge-based NAAT that simultaneously detects M. tuberculosis complex and rifampin resistance within 2 hours directly from clinical specimens. It targets the rpoB gene and has revolutionized TB diagnosis globally. It is particularly valuable in Canadian settings for rapid diagnosis and public health response.

Question 110: A D-negative woman delivers a D-positive baby and the Kleihauer-Betke test shows 1.5% fetal cells. How many vials of RhIg (300 µg) should be administered?

5 vials
1 vial
2 vials
3 vials (Correct answer)

Correct answer: 3 vials

Calculation: 1.5% fetal cells × 5000 mL (estimated maternal blood volume) = 75 mL fetal whole blood. Convert to mL of fetal red cells: 75 × 0.5 (hematocrit) = 37.5 mL RBCs. Each 300 µg vial covers 30 mL of fetal red cells. 37.5/30 = 1.25, round up to 2, then add 1 safety vial = 3 vials. (Some institutions use the formula: divide mL fetal bleed by 30, round up, add 1.)

Question 111: Which hormone is measured using a stimulation test with cosyntropin (synthetic ACTH)?

Cortisol (Correct answer)
Testosterone
Aldosterone
Growth hormone

Correct answer: Cortisol

The cosyntropin stimulation test measures cortisol response to synthetic ACTH to assess adrenal gland function. A normal response shows cortisol rising above 500 nmol/L, while an inadequate response suggests primary adrenal insufficiency (Addison disease).

Question 112: A serum separator tube (SST) is received for routine chemistry testing. According to CLSI guidelines, what is the recommended maximum time between collection and centrifugation to ensure specimen integrity?

2 hours (Correct answer)
4 hours
30 minutes
6 hours

Correct answer: 2 hours

To ensure the quality and integrity of the specimen, CLSI guidelines recommend that serum separator tubes be centrifuged within 2 hours of collection. Delay beyond this timeframe can lead to changes in analyte concentrations due to ongoing cellular metabolism.

Question 113: Which hereditary condition causes increased osmotic fragility of red blood cells?

Thalassemia
Sickle cell disease
G6PD deficiency
Hereditary spherocytosis (Correct answer)

Correct answer: Hereditary spherocytosis

Hereditary spherocytosis causes increased osmotic fragility because the spherical red blood cells have decreased surface-area-to-volume ratio and cannot swell as much before lysing in hypotonic solutions. The osmotic fragility test and eosin-5-maleimide (EMA) binding test are used to confirm the diagnosis.

Question 114: A patient is scheduled for a Prothrombin Time (PT/INR), a Complete Blood Count (CBC), and a glucose test. Following the CLSI recommended order of draw, which tube should be collected second?

Lavender top (EDTA)
Gray top (Sodium Fluoride/Potassium Oxalate)
Red top (Clot activator)
Light Blue top (Sodium Citrate) (Correct answer)

Correct answer: Light Blue top (Sodium Citrate)

The correct order of draw is crucial to prevent cross-contamination of additives between tubes. According to CLSI guidelines, the sequence is: 1) Blood cultures, 2) Light Blue top (for coagulation tests like PT/INR), 3) Serum tubes (Red/Gold), 4) Heparin tubes (Green), 5) EDTA tubes (Lavender for CBC), and finally 6) Glycolytic inhibitor tubes (Gray for glucose). Therefore, the Light Blue top tube is collected second in this scenario.

Question 115: What is urine protein electrophoresis used for?

Characterizing the type of proteinuria (glomerular vs. tubular vs. overflow) and detecting Bence Jones protein (Correct answer)
Measuring total urine protein only
Testing for glucose in urine
Routine screening for proteinuria

Correct answer: Characterizing the type of proteinuria (glomerular vs. tubular vs. overflow) and detecting Bence Jones protein

Urine protein electrophoresis separates urinary proteins to determine the pattern: glomerular proteinuria (albumin predominance), tubular proteinuria (low-molecular-weight proteins like beta-2 microglobulin), overflow proteinuria (abnormal proteins like Bence Jones), and mixed patterns. It is essential for detecting monoclonal light chains not found on routine dipstick.

Question 116: A cerebrospinal fluid (CSF) specimen is delivered to the lab for cell count, microbiology, and chemistry tests. The sample consists of four sequentially collected sterile tubes, numbered 1 through 4. For the cell count and differential, which tube is typically preferred to minimize contamination from a traumatic tap?

Tube #1
Tube #4 (Correct answer)
Any tube can be used interchangeably
Tube #2

Correct answer: Tube #4

In a lumbar puncture, the first tube collected may be contaminated with peripheral blood from the puncture itself. Subsequent tubes will have progressively fewer red blood cells if the bleeding was from a traumatic tap. Therefore, the last tube collected (Tube #3 or #4) is preferred for cell counts and cytology to get the most accurate representation of the cells actually present in the CSF.

Question 117: A complaint is filed with the CMLTO against a registered MLT. What is the first step in the CMLTO complaints process?

The complaint is forwarded directly to the MLT's employer
The MLT's registration is automatically suspended pending investigation
A formal Discipline Committee hearing is scheduled immediately
The Complaints Committee reviews the complaint and investigates to determine if it should be referred to Discipline or resolved otherwise (Correct answer)

Correct answer: The Complaints Committee reviews the complaint and investigates to determine if it should be referred to Discipline or resolved otherwise

The Complaints Committee receives and investigates complaints against CMLTO members, determining whether allegations meet the threshold for referral to the Discipline Committee or can be resolved through other means.

Question 118: A laboratory's glucose analyzer has a reportable range of 1.0–30.0 mmol/L. A patient result reads 'HI' (above the linear range). The technologist dilutes the specimen 1:4 with saline and obtains a result of 9.8 mmol/L. What is the corrected patient glucose?

44.0 mmol/L
9.8 mmol/L
39.2 mmol/L (Correct answer)
2.45 mmol/L

Correct answer: 39.2 mmol/L

Corrected result = Diluted result × Dilution factor = 9.8 × 4 = 39.2 mmol/L.

Question 119: What is the significance of measuring C-reactive protein (CRP) in clinical chemistry?

Evaluating thyroid function
Measuring complement activation
Assessing nutritional status
Detecting and monitoring inflammation and infection (Correct answer)

Correct answer: Detecting and monitoring inflammation and infection

CRP is an acute phase protein produced by the liver in response to inflammation. It rises rapidly (within 6-8 hours) and can increase up to 1000-fold during acute infection or inflammation. High-sensitivity CRP (hs-CRP) is also used for cardiovascular risk assessment.

Question 120: What technique is used to separate DNA fragments by size during gel electrophoresis?

Precipitation by salt concentration
Centrifugation based on molecular density
Migration through an agarose gel matrix under an electrical current (Correct answer)
Filtration through a molecular sieve membrane

Correct answer: Migration through an agarose gel matrix under an electrical current

DNA fragments migrate through an agarose gel under electrical current — smaller fragments move faster through the gel matrix than larger fragments, separating them by size.

Question 121: A physician in the ER performs a lumbar puncture on a patient. Which of the following tests are likely to be ordered?

Glucose, protein, Gram's stain, cell count (Correct answer)
CBC, PT, PTT
AST, ALT, Alk. Phos
INR, Urea, lytes, creatinine
Group and screen and crossmatch

Correct answer: Glucose, protein, Gram's stain, cell count

When a physician performs a lumbar puncture to collect cerebrospinal fluid (CSF), the primary tests ordered are typically for diagnosing infections, inflammation, or other neurological conditions. Therefore, a cell count (to check for increased white blood cells), glucose and protein levels (to assess for infection or inflammation), and a Gram's stain (to identify bacterial pathogens) are standard and crucial analyses performed on CSF.

Question 122: A patient with known anti-E requires 2 units of red blood cells for surgery. How should compatible blood be provided?

Any ABO/Rh-compatible blood is acceptable
Use O-negative blood without crossmatch
Only autologous blood can be used
Select E-negative, ABO/Rh-compatible units and perform an antiglobulin crossmatch (Correct answer)

Correct answer: Select E-negative, ABO/Rh-compatible units and perform an antiglobulin crossmatch

For a patient with anti-E, E-antigen-negative donor units must be selected. ABO and Rh(D) compatibility is also required. Since the patient has a clinically significant antibody, an antiglobulin crossmatch (not electronic crossmatch) must be performed to confirm serological compatibility. The antibody history must be maintained permanently in the patient's transfusion record.

Question 123: What is the purpose of a biological safety cabinet (BSC) Class II Type A2 in a medical laboratory?

Protection of personnel only from aerosols
Containment of radioactive materials
Protection of personnel, product, and environment from biohazardous aerosols (Correct answer)
Protection of the product and environment only

Correct answer: Protection of personnel, product, and environment from biohazardous aerosols

A Class II Type A2 BSC provides triple protection: personnel protection, product protection, and environmental protection by recirculating and exhausting HEPA-filtered air.

Question 124: A CSF specimen has elevated protein, low glucose, elevated WBC with neutrophil predominance, and the Gram stain shows gram-negative diplococci. What is the most likely pathogen?

Streptococcus pneumoniae
Listeria monocytogenes
Haemophilus influenzae
Neisseria meningitidis (Correct answer)

Correct answer: Neisseria meningitidis

Gram-negative diplococci (kidney-bean shaped) in CSF with a bacterial meningitis profile (high protein, low glucose, neutrophilic pleocytosis) is classic for Neisseria meningitidis. This is a medical emergency requiring immediate ceftriaxone therapy and close contact prophylaxis with rifampin or ciprofloxacin. It is reportable to public health.

Question 125: Which blood culture system is most commonly used in Canadian clinical laboratories?

Manual biphasic bottles
Pour plate method
Lysis-centrifugation (Isolator)
Automated continuous-monitoring blood culture systems (BacT/ALERT or BACTEC) (Correct answer)

Correct answer: Automated continuous-monitoring blood culture systems (BacT/ALERT or BACTEC)

Automated continuous-monitoring blood culture systems (such as bioMérieux BacT/ALERT and Becton Dickinson BACTEC) are the standard in Canadian laboratories. These systems continuously monitor bottles for CO2 production or pH changes indicating microbial growth, providing rapid detection (average 12-36 hours for common pathogens).

Question 126: The Weil-Felix test uses Proteus vulgaris antigens to detect antibodies in patients suspected of having:

Rickettsial infections (Correct answer)
Lyme disease
Syphilis
Brucellosis

Correct answer: Rickettsial infections

The Weil-Felix test exploits cross-reactive antigens between Rickettsia species and certain Proteus strains; patient antibodies from rickettsial infections agglutinate Proteus OX-19, OX-2, and OX-K antigens.

Question 127: What is the purpose of the discriminator setting on a hematology analyzer for cell counting?

To set the temperature for cell lysis
To calibrate the detector for specific cell types
To set the maximum cell count per analysis
To define voltage thresholds that distinguish cell populations by size or electrical impedance (Correct answer)

Correct answer: To define voltage thresholds that distinguish cell populations by size or electrical impedance

Discriminators are electronic threshold settings on hematology analyzers that define boundaries between cell populations (e.g., between RBCs and platelets, or between WBC populations) based on electrical impedance or light scatter characteristics.

Question 128: Which of the following is a correct practice when labelling patient specimens in the laboratory?

Labels can be added later by laboratory staff if the collection team forgets
Electronic labels are not required as long as handwritten labels are present
Specimens must be labelled at the patient's bedside immediately after collection with two patient identifiers (Correct answer)
Labels may be applied before collection to save time if the patient's name is known

Correct answer: Specimens must be labelled at the patient's bedside immediately after collection with two patient identifiers

Specimens must be labelled at the point of collection immediately after collection, using at least two patient identifiers (name, date of birth, or health card number), to prevent misidentification.

Question 129: A urine specimen from a child has a positive dipstick for blood and protein. Microscopy shows RBC casts and dysmorphic red blood cells. Serum complement C3 is low. What diagnosis should be suspected?

Nephrotic syndrome
Urinary tract infection
Post-streptococcal glomerulonephritis (Correct answer)
Bladder trauma

Correct answer: Post-streptococcal glomerulonephritis

RBC casts (proving glomerular origin of hematuria), dysmorphic RBCs, proteinuria, and low serum complement (C3 consumption via the alternative pathway) in a child are classic for post-streptococcal glomerulonephritis. This immune-complex mediated disease typically follows a group A streptococcal pharyngitis or skin infection by 1-3 weeks. ASO titer and anti-DNase B confirm recent streptococcal infection.

Question 130: A urine culture grows more than 100,000 CFU/mL of a single organism. What does this indicate?

Contamination
Normal flora
Significant bacteriuria consistent with urinary tract infection (Correct answer)
Specimen collection error

Correct answer: Significant bacteriuria consistent with urinary tract infection

Growth of ≥10⁵ CFU/mL (100,000 CFU/mL) of a single organism from a clean-catch midstream urine is considered significant bacteriuria. This threshold, combined with clinical symptoms, supports the diagnosis of UTI. Lower counts may be significant in catheterized specimens or symptomatic patients.

Question 131: Which hemoglobin variant migrates in the same position as HbS on alkaline electrophoresis?

HbH
HbE
HbC
HbD and HbG (Correct answer)

Correct answer: HbD and HbG

HbD and HbG migrate in the same position as HbS on alkaline (cellulose acetate) electrophoresis at pH 8.6. To differentiate these variants, a second method such as acid electrophoresis (citrate agar at pH 6.2) or HPLC is required, as they separate differently under acidic conditions.

Question 132: Which of the following reagents is used for blueing a hematoxylin-stained section?

Mordant solution
Alkaline solution (Correct answer)
Methylene blue solution
Acid solution
Alcohol solution

Correct answer: Alkaline solution

After hematoxylin staining, tissue sections typically appear reddish-purple. To achieve the desired blue color, which provides optimal nuclear staining and contrast, the sections are treated with an alkaline solution, a process known as 'blueing.' The alkaline environment converts the reddish-purple hematoxylin dye into a stable, insoluble blue lake.

Question 133: In medical terminology, the suffix '-centesis' refers to what type of procedure?

Surgical removal of an organ
Creation of an opening
Visualization using a scope
Surgical puncture to remove fluid (Correct answer)

Correct answer: Surgical puncture to remove fluid

'-centesis' means surgical puncture to aspirate or remove fluid. Examples include thoracentesis (chest fluid), paracentesis (abdominal fluid), and arthrocentesis (joint fluid).

Question 134: When is it necessary to collect a trough level for therapeutic drug monitoring (TDM) of vancomycin?

At any time, as vancomycin levels are constant throughout the dosing interval
30 minutes after the start of the vancomycin infusion
Immediately before the next scheduled vancomycin dose (Correct answer)
2 hours after the infusion is complete

Correct answer: Immediately before the next scheduled vancomycin dose

Vancomycin trough levels are collected immediately before the next scheduled dose (at the lowest point in the dosing interval) to assess drug accumulation, dosing adequacy, and risk of toxicity.

Question 135: During arterial blood gas (ABG) collection, what is the minimum time pressure must be applied to the radial artery puncture site after needle withdrawal in a patient not on anticoagulants?

10-15 minutes
1-2 minutes
Only until bleeding visibly stops
3-5 minutes (Correct answer)

Correct answer: 3-5 minutes

A minimum of 3-5 minutes of firm pressure must be applied to arterial puncture sites in patients not on anticoagulants to prevent hematoma formation, given the higher pressure of arterial blood flow.

Question 136: A cerebrospinal fluid (CSF) specimen is collected by lumbar puncture. What is the correct handling priority for this specimen in the laboratory?

Centrifuge and freeze all aliquots before analysis
Refrigerate and batch with routine specimens
Store at 4°C and process within 4 hours
Process immediately and never refrigerate (Correct answer)

Correct answer: Process immediately and never refrigerate

CSF is a critical specimen that must be processed immediately. Refrigeration kills fragile organisms (like Neisseria meningitidis) and degrades cells, making immediate processing essential.

Question 137: What is the clinical significance of an elevated serum lipase compared to amylase in suspected pancreatitis?

Lipase remains elevated longer and is more specific for pancreatic injury (Correct answer)
Lipase is less specific for pancreatic disease
Amylase is always preferred over lipase
Lipase is only elevated in chronic pancreatitis

Correct answer: Lipase remains elevated longer and is more specific for pancreatic injury

Serum lipase is more specific for pancreatic disease than amylase and remains elevated for a longer duration (up to 14 days vs 3-5 days for amylase). Many Canadian guidelines now recommend lipase as the preferred single test for diagnosing acute pancreatitis.

Question 138: Which of the following is considered the most effective method for verifying that a steam autoclave cycle has successfully achieved sterilization?

Processing a biological indicator containing Geobacillus stearothermophilus spores (Correct answer)
Using heat-sensitive autoclave tape on the exterior of the packages
Placing a chemical indicator strip in the center of the load
Observing that the pressure and temperature gauges reached the required settings

Correct answer: Processing a biological indicator containing Geobacillus stearothermophilus spores

Biological indicators containing highly resistant bacterial spores, such as Geobacillus stearothermophilus, are the gold standard for validating sterilization. A successful cycle is confirmed when these spores are killed and fail to grow upon incubation. Chemical indicators and physical readings only confirm that certain conditions were met, not that sterilization was effective.

Question 139: Which antibodies are considered clinically significant in transfusion medicine?

Only ABO antibodies
Only cold-reactive IgM antibodies
All antibodies are equally significant
IgG antibodies reactive at 37°C that can cause hemolytic transfusion reactions or HDFN (anti-D, anti-K, anti-Fy(a), anti-Jk(a), etc.) (Correct answer)

Correct answer: IgG antibodies reactive at 37°C that can cause hemolytic transfusion reactions or HDFN (anti-D, anti-K, anti-Fy(a), anti-Jk(a), etc.)

Clinically significant antibodies are typically IgG, react at 37°C, and can activate complement or cause extravascular hemolysis. Examples include anti-D, anti-c, anti-E, anti-K, anti-Fy(a), anti-Jk(a), and anti-S. These antibodies require antigen-negative, crossmatch-compatible blood for transfusion. Cold-reactive IgM antibodies (anti-M, anti-N, anti-P1) are usually clinically insignificant.

Question 140: Which staining method is used to identify Pneumocystis jirovecii in respiratory specimens?

Wright-Giemsa stain only
Gram stain
Acid-fast stain
Gomori methenamine silver (GMS) stain or immunofluorescence (Correct answer)

Correct answer: Gomori methenamine silver (GMS) stain or immunofluorescence

Gomori methenamine silver (GMS) stain highlights the cyst wall of Pneumocystis jirovecii as dark brown/black against a green background. Direct fluorescent antibody (DFA) testing is more sensitive and specific. PCR is increasingly used as it can detect both cystic and trophic forms. P. jirovecii causes pneumonia in immunocompromised patients.

Question 141: What is the clinical significance of an elevated serum amylase level?

Renal failure
Hypothyroidism
Acute pancreatitis (Correct answer)
Congestive heart failure

Correct answer: Acute pancreatitis

Elevated serum amylase is most commonly associated with acute pancreatitis. Amylase is released from damaged pancreatic acinar cells into the bloodstream. However, amylase can also be elevated in other conditions such as salivary gland disorders and intestinal obstruction.

Question 142: What does a 'left shift' in the white blood cell differential indicate?

An increase in eosinophils
An increase in mature lymphocytes
An increase in immature granulocytes (bands and metamyelocytes) indicating active infection (Correct answer)
A decrease in all white blood cell types

Correct answer: An increase in immature granulocytes (bands and metamyelocytes) indicating active infection

A left shift refers to an increase in immature granulocytes (particularly band neutrophils, but also metamyelocytes and myelocytes) in peripheral blood. This indicates the bone marrow is releasing cells prematurely in response to increased demand, typically from bacterial infection or inflammation.

Question 143: Which stain is used to identify iron stores in bone marrow aspirates?

Periodic acid-Schiff (PAS) stain
Sudan black B stain
Prussian blue (Perls) stain (Correct answer)
Wright-Giemsa stain

Correct answer: Prussian blue (Perls) stain

Prussian blue (Perls) stain reacts with ferric iron (Fe3+) in hemosiderin to produce a blue-green color. It is used to assess iron stores in bone marrow macrophages and to identify sideroblasts (erythroblasts containing iron granules). Absent stainable iron confirms iron deficiency.

Question 144: What is Beer's Law and how does it apply to clinical chemistry?

It states that absorbance is directly proportional to the concentration of the absorbing substance and path length (Correct answer)
It describes the relationship between temperature and reaction rate
It describes the equilibrium between bound and free drug
It defines the relationship between pH and pKa

Correct answer: It states that absorbance is directly proportional to the concentration of the absorbing substance and path length

Beer's Law (A = εbc) states that absorbance is directly proportional to the molar absorptivity (ε), path length (b), and concentration (c) of the absorbing substance. This is the fundamental principle underlying spectrophotometric measurements in clinical chemistry, allowing concentration to be determined from absorbance readings.

Question 145: A patient has hemoglobin 95 g/L, MCV 72 fL, HbA2 5.8%, and normal iron studies. What is the most likely diagnosis?

Alpha-thalassemia trait
Beta-thalassemia trait (Correct answer)
Anemia of chronic disease
Iron deficiency anemia

Correct answer: Beta-thalassemia trait

Microcytic anemia with elevated HbA2 (>3.5%) and normal iron studies is the classic pattern for beta-thalassemia trait. The reduced beta-globin chain production leads to a relative excess of delta-chains, increasing HbA2. Iron studies are normal because the anemia is not due to iron deficiency.

Question 146: In the coagulation cascade, which pathway is activated by tissue factor released from damaged tissue?

Extrinsic pathway (tissue factor pathway) (Correct answer)
Fibrinolytic pathway
Intrinsic pathway (contact activation)
Common pathway only

Correct answer: Extrinsic pathway (tissue factor pathway)

The extrinsic pathway is initiated by tissue factor (factor III) released from damaged cells outside the blood vessel, which activates factor VII to begin the coagulation cascade.

Question 147: What does the term 'hemolysis' mean in the context of laboratory specimen quality?

Bacterial contamination of the specimen
Clotting of blood in the collection tube
Rupture of red blood cells releasing hemoglobin into the plasma/serum (Correct answer)
Protein denaturation during storage

Correct answer: Rupture of red blood cells releasing hemoglobin into the plasma/serum

Hemolysis refers to rupture of red blood cell membranes with release of intracellular contents including hemoglobin into the serum or plasma, causing a pink or red discolouration.

Question 148: Which test is used to assess platelet function?

Platelet aggregation studies using light transmission aggregometry (Correct answer)
Prothrombin time
Factor XIII assay
Thrombin time

Correct answer: Platelet aggregation studies using light transmission aggregometry

Light transmission aggregometry (LTA) is the gold standard for assessing platelet function. Platelet-rich plasma is stimulated with various agonists (ADP, collagen, epinephrine, arachidonic acid, ristocetin) and the change in light transmission is measured as platelets aggregate. Abnormal patterns help diagnose platelet function disorders.

Question 149: An MLA/T receives a blood specimen for a Prothrombin Time (PT) test in a light blue top tube. The MLA/T observes that the tube is only filled to 50% of its capacity. What is the implication of this short draw?

The results will be falsely prolonged (higher). (Correct answer)
The results will be falsely shortened (lower).
The specimen will likely be hemolyzed.
There is no significant impact on the test results.

Correct answer: The results will be falsely prolonged (higher).

Light blue (sodium citrate) tubes used for coagulation testing require a specific 9:1 blood-to-anticoagulant ratio. An underfilled tube contains an excess of the citrate anticoagulant relative to the amount of blood, which will bind more calcium than necessary and lead to falsely prolonged clotting times for tests like PT and aPTT.

Question 150: What is phenotype matching and when is it clinically important?

Matching based on patient age and weight
Extended antigen matching beyond ABO/Rh(D) to prevent alloimmunization in patients requiring chronic transfusions (Correct answer)
Only required for autologous donations
Matching only ABO and Rh(D)

Correct answer: Extended antigen matching beyond ABO/Rh(D) to prevent alloimmunization in patients requiring chronic transfusions

Phenotype matching involves selecting donor red cells that match the patient's extended red cell antigen profile (typically Rh (C, c, E, e) and Kell, sometimes Duffy, Kidd, and MNS). It is particularly important for patients with sickle cell disease, thalassemia, and other conditions requiring chronic transfusion to reduce alloimmunization risk.

Question 151: According to the Canadian Biosafety Standard (CBS), a laboratory routinely handling clinical specimens containing Mycobacterium tuberculosis, an agent that can cause serious disease and is transmissible by inhalation, must operate at which minimum Containment Level (CL)?

Containment Level 4 (CL4)
Containment Level 3 (CL3) (Correct answer)
Containment Level 1 (CL1)
Containment Level 2 (CL2)

Correct answer: Containment Level 3 (CL3)

Mycobacterium tuberculosis is a Risk Group 3 (RG3) human pathogen, defined as having a high individual risk and low community risk. [5] Work with indigenous or exotic agents that can cause serious or potentially lethal disease through the inhalation route must be conducted in a Containment Level 3 (CL3) laboratory. [21] This level requires specific engineering controls and operational practices to protect personnel and the community. [5, 12]

MLPAO MLA/T Certification Exam

The MLPAO MLA/T certification exam tests medical laboratory assistants/technicians in clinical chemistry, hematology, microbiology, transfusion medicine, specimen collection, laboratory safety, and professional practice.

150

Questions

180 min

Time Limit

60%

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