Certified Phlebotomy Technician Exam Special Specimen Collections 5 — Questions and Answers
Question 1: When collecting a specimen for a prothrombin time (PT) or aPTT, what is the critical fill requirement for the sodium citrate (blue-top) tube?
- Fill to at least 50% of tube capacity
- Fill exactly to the line — the 9:1 blood-to-citrate ratio must be maintained (Correct answer)
- Fill no more than 75% to prevent clotting
- Fill level does not affect coagulation results
Correct answer: Fill exactly to the line — the 9:1 blood-to-citrate ratio must be maintained
The 9:1 blood-to-anticoagulant ratio is critical for coagulation testing; under- or overfilling alters the ratio and produces inaccurate PT/aPTT results.
Question 2: A phlebotomist is asked to collect a specimen for lead testing. Which tube is most appropriate?
- SST (gold/red-gray)
- Sodium fluoride gray-top
- Trace-element-free royal blue-top or tan-top EDTA (Correct answer)
- Standard lavender-top EDTA
Correct answer: Trace-element-free royal blue-top or tan-top EDTA
Trace element and heavy metal testing requires royal blue-top or tan-top EDTA tubes certified to be free of metal contaminants that could falsely elevate results.
Question 3: Which specimen collection is used for a hemoglobin A1c (HbA1c) test and why is fasting NOT required?
- Plasma from an SST; fasting changes A1c acutely
- Whole blood EDTA; A1c reflects average glucose over 2–3 months, not recent intake (Correct answer)
- Serum; fasting is required for all glucose-related tests
- Urine dipstick; fasting affects urine glucose differently
Correct answer: Whole blood EDTA; A1c reflects average glucose over 2–3 months, not recent intake
HbA1c measures glycated hemoglobin, which reflects the average blood glucose over the lifespan of red blood cells (approximately 2–3 months), so recent food intake has no meaningful effect.
Question 4: A patient's arterial blood gas (ABG) is drawn from the radial artery. Which pre-procedure assessment is mandatory?
- Palpating the femoral pulse
- Performing the Allen test to assess collateral ulnar circulation (Correct answer)
- Applying a tourniquet 2 inches above the wrist
- Checking the patient's INR level first
Correct answer: Performing the Allen test to assess collateral ulnar circulation
The Allen test is performed before radial ABG to confirm adequate ulnar collateral circulation, ensuring blood flow to the hand if the radial artery is damaged.
Question 5: Which of the following specimens requires protection from light during transport?
- Blood culture bottles
- Bilirubin and porphyrin specimens (Correct answer)
- Coagulation specimens
- Blood urea nitrogen (BUN) specimens
Correct answer: Bilirubin and porphyrin specimens
Bilirubin and porphyrins are photosensitive compounds that degrade rapidly when exposed to light, requiring amber containers or aluminum foil wrapping during transport.
Question 6: When is a lavender-top (EDTA) tube preferred over a serum tube for blood bank testing?
- EDTA is never used for blood bank; serum is always required
- For type and screen or crossmatch, EDTA whole blood is required because EDTA preserves RBC antigens (Correct answer)
- EDTA is only used for blood bank in pediatric patients
- Either tube is acceptable for all blood bank procedures
Correct answer: For type and screen or crossmatch, EDTA whole blood is required because EDTA preserves RBC antigens
Blood bank testing such as type and screen uses EDTA whole blood because the anticoagulant preserves red blood cell surface antigens needed for antibody detection.
Question 7: For a urine culture collected by midstream clean-catch, the specimen must be delivered to the lab within what timeframe if not refrigerated?
- 30 minutes
- 2 hours (Correct answer)
- 6 hours
- 12 hours
Correct answer: 2 hours
Urine for culture must reach the lab within 2 hours at room temperature; beyond that, bacteria multiply and distort quantitative culture results.
Certified Phlebotomy Technician Exam Special Specimen Collections 5
When collecting a specimen for a prothrombin time (PT) or aPTT, what is the critical fill requirement for the sodium citrate (blue-top) tube?