Certified Phlebotomy Technician Exam Basic 4 — Questions and Answers
Question 1: A phlebotomist notices that a collected SST tube has visible clots after centrifugation. What most likely caused this?
- Too few inversions after collection (Correct answer)
- Using a 21-gauge needle
- Labeling the tube before centrifugation
- Drawing the tube after the EDTA tube
Correct answer: Too few inversions after collection
Insufficient mixing after collection prevents the clot activator in an SST from working uniformly, leading to fibrin clots in the serum.
Question 2: What is the maximum recommended time a tourniquet should remain applied before venipuncture?
- 30 seconds
- 1 minute (Correct answer)
- 2 minutes
- 5 minutes
Correct answer: 1 minute
CLSI guidelines recommend tourniquet application for no longer than 1 minute to avoid hemoconcentration and analyte changes.
Question 3: Which lab test requires a 2:1 blood-to-additive ratio in the collection tube?
- CBC (complete blood count)
- Prothrombin time (PT) (Correct answer)
- Basic metabolic panel
- Hemoglobin A1c
Correct answer: Prothrombin time (PT)
Coagulation tubes (light-blue tops) require a precise 9:1 blood-to-sodium citrate ratio; underfilling the tube dilutes the anticoagulant and falsely prolongs clotting times.
Question 4: A patient is taking warfarin (Coumadin). Which tube should be drawn for therapeutic monitoring?
- Green-top (heparin)
- Lavender-top (EDTA)
- Light-blue top (sodium citrate) (Correct answer)
- Gray-top (fluoride/oxalate)
Correct answer: Light-blue top (sodium citrate)
Warfarin therapy is monitored via PT/INR, which requires a sodium citrate (light-blue top) tube to preserve coagulation factor activity.
Question 5: What is the correct response when a patient states they have a latex allergy before venipuncture?
- Proceed normally because modern gloves are all nitrile
- Use latex-free gloves, tourniquets, and supplies throughout the procedure (Correct answer)
- Ask the patient to rate the severity before deciding on precautions
- Notify the charge nurse but continue using available supplies
Correct answer: Use latex-free gloves, tourniquets, and supplies throughout the procedure
A reported latex allergy requires replacing all latex-containing items with latex-free alternatives to prevent an allergic reaction.
Question 6: In the order of draw, why are coagulation tubes (light-blue) drawn before other additive tubes?
- To prevent sodium citrate from contaminating other tubes
- To avoid tissue thromboplastin from altering coagulation results (Correct answer)
- Because they require the most blood volume
- To allow the longest clotting time before serum tests
Correct answer: To avoid tissue thromboplastin from altering coagulation results
Tissue thromboplastin released during skin puncture can activate coagulation; drawing the coagulation tube early (after a discard tube when using a butterfly) minimizes this contamination.
Question 7: Which of the following specimens requires protection from light during transport?
- Prothrombin time sample
- Bilirubin specimen (Correct answer)
- Hemoglobin A1c sample
- Basic metabolic panel specimen
Correct answer: Bilirubin specimen
Bilirubin is photosensitive and degrades rapidly when exposed to light, so specimens must be wrapped in foil or placed in an amber bag.
Certified Phlebotomy Technician Exam Basic 4
A phlebotomist notices that a collected SST tube has visible clots after centrifugation.
What most likely caused this?