Mixed Deck — All MLS Topics Flashcards

Which of the following is a critical component of a laboratory’s quality assurance (QA) program?

Answer: Proficiency testing

Proficiency testing is a key part of quality assurance, helping to evaluate a laboratory’s ability to produce accurate and consistent test results.

Which anticoagulant is used in the light blue (sodium citrate) tube and what is its primary application?

Answer: Sodium citrate; coagulation studies

Sodium citrate chelates calcium to prevent clotting and is the required anticoagulant for PT, aPTT, and other coagulation assays.

A pediatric patient with acute lymphoblastic leukemia (ALL) on maintenance therapy has an ANC of 450/µL. Per standard protocol management, the MOST appropriate action is:

Answer: Hold methotrexate and 6-MP; recheck CBC in one week

ALL maintenance protocols hold antimetabolites (MTX and 6-MP) when ANC falls below 500–750/µL to prevent life-threatening neutropenia, with CBC recheck to guide restart.

A urine culture grows >100,000 CFU/mL of a lactose-fermenting gram-negative rod. Oxidase is negative. Most likely organism is:

Answer: Escherichia coli

E. coli is oxidase-negative, lactose-fermenting, and is the most common cause of community-acquired urinary tract infections at significant colony counts.

Which action is required when a pipette calibration check shows a systematic error of 3% at all volume settings?

Answer: Remove the pipette from service and recalibrate or repair it

A systematic 3% error at all volumes exceeds most laboratory tolerance limits and requires the pipette to be removed from service for recalibration or repair.

During a flooding emergency in the laboratory basement where specimens are processed, the FIRST priority for the MLS on duty is:

Answer: Personal safety and evacuation of all personnel

Personal safety and evacuation of personnel is always the first priority in any emergency before addressing equipment, specimens, or data.

A laboratory centrifuge tube containing an unknown specimen breaks during a run. After stopping the centrifuge, what is the next correct action before opening the lid?

Answer: Wait at least 30 minutes with the centrifuge closed to allow aerosol settling, then open in a biosafety cabinet

A 30-minute wait allows aerosols containing potentially infectious material to settle before the lid is opened, and BSC use prevents further exposure.

An MLS receives a requisition with illegible handwriting for the test ordered. What should be done?

Answer: Contact the ordering clinician for clarification before processing

Illegible orders must be clarified with the ordering clinician to prevent errors and ensure the correct test is performed.

A new rapid influenza test is being evaluated against viral culture. Sensitivity is 70% and specificity is 99%. What does the low sensitivity mean in practice?

Answer: 30% of true influenza cases will test negative (false negatives)

Sensitivity of 70% means 30% of patients who truly have influenza will receive a false-negative result and may go undiagnosed and untreated.

A critically ill patient has an ionized calcium of 0.78 mmol/L (reference: 1.15–1.35 mmol/L) after massive transfusion. The MOST likely cause and treatment is:

Answer: Citrate-chelation of calcium from preservative in blood products; administer IV calcium

Citrate in blood product preservatives chelates ionized calcium; massive transfusion can cause clinically significant hypocalcemia requiring IV calcium gluconate or chloride.

A positive Direct Antiglobulin Test (DAT) indicates that:

Answer: The patient's red blood cells are coated with IgG or complement in vivo

A positive DAT demonstrates that the patient's circulating red blood cells are sensitized (coated) with IgG antibodies or complement components in vivo.

Which directional term means toward the front of the body?

Answer: Anterior

Anterior (or ventral) refers to the front surface of the body.

A laboratory scientist discovers a mercury thermometer has broken and spilled in the chemistry section. The correct response is to:

Answer: Evacuate the area and use a mercury spill kit according to policy

Mercury requires a specialized spill kit; vacuuming aerosolizes it and bleach does not neutralize it — the area must be evacuated and the kit used per policy.

Which of the following is a key marker used to diagnose myocardial infarction?

Answer: Troponin

Troponin is a highly specific and sensitive biomarker for myocardial infarction (heart attack). When heart muscle is damaged due to ischemia, troponin proteins are released into the bloodstream. Elevated levels of cardiac troponin (T or I) indicate myocardial injury, making it the preferred diagnostic marker in clinical practice for confirming a heart attack.

A patient with acute promyelocytic leukemia (APL) is started on ATRA therapy. Which potentially fatal complication should be monitored with daily CBC and coagulation studies?

Answer: Differentiation syndrome and DIC

APL carries high risk of DIC from granule release, and ATRA differentiation syndrome (respiratory distress, fever, effusions) can be fatal; both require vigilant lab monitoring.

A laboratory result is reported with a delta check flag. This means:

Answer: The result differs significantly from the patient's previous value

A delta check compares the current result to the patient's most recent prior result; a flag indicates a change exceeding the defined limit, alerting staff to possible error or acute clinical change.

Which of the following is the preferred specimen for detecting Clostridioides difficile toxin?

Answer: Unformed (liquid or soft) stool

C. difficile testing should only be performed on unformed stool, as formed stool from asymptomatic carriers gives false-positive results and does not indicate active colitis.

A lab receives a request for a STAT troponin on a patient in the ED. The tube arrives unlabeled. What should the MLS do?

Answer: Reject the specimen and document per policy

Unlabeled specimens must be rejected per CLSI and accreditation standards because mislabeling errors can cause patient harm; the ED must recollect with proper labeling.

An anion gap of 24 mEq/L (reference 8–16) with low bicarbonate and normal chloride best indicates:

Answer: High anion gap metabolic acidosis

An elevated anion gap with metabolic acidosis indicates accumulation of unmeasured anions such as lactate, ketones, uremic acids, or salicylate.

Which biological safety level (BSL) designation requires both a self-contained suit with a supplied air source and a dedicated decontamination shower?

Answer: BSL-4

BSL-4 laboratories handle the most dangerous pathogens and require full-body positive-pressure suits with supplied air for maximum worker protection.