Phlebotomy Test Specimen Processing and Handling 3 — Questions and Answers
Question 1: Which of the following best describes the correct technique for mixing an EDTA tube after venipuncture?
- Shake vigorously for 10 seconds
- Gently invert 8–10 times (Correct answer)
- Leave undisturbed for 5 minutes then invert once
- Vortex at low speed for 30 seconds
Correct answer: Gently invert 8–10 times
EDTA tubes should be gently inverted 8–10 times immediately after collection to ensure thorough anticoagulant mixing without causing hemolysis.
Question 2: Why must lithium heparin tubes NOT be used for lithium level tests?
- Heparin destroys lithium ions
- The additive lithium will falsely elevate the patient's lithium result (Correct answer)
- Heparin causes lithium to precipitate
- Lithium levels require serum, not plasma
Correct answer: The additive lithium will falsely elevate the patient's lithium result
The lithium in lithium heparin additive would be added to the patient's own lithium, causing a falsely elevated serum lithium measurement.
Question 3: A specimen tube that should be kept on ice during transport is a(n):
- CBC (complete blood count) tube
- Arterial blood gas (ABG) syringe (Correct answer)
- Coagulation (PT/INR) tube
- Blood culture bottle
Correct answer: Arterial blood gas (ABG) syringe
ABG samples must be kept on ice to slow cellular metabolism and prevent gas exchange that would alter pH, pO₂, and pCO₂ values.
Question 4: What is the purpose of the separator gel found in SST (serum separator) tubes?
- It acts as a clot activator to speed clotting
- It forms a stable barrier between serum and clot after centrifugation (Correct answer)
- It prevents hemolysis during collection
- It keeps the specimen frozen during transport
Correct answer: It forms a stable barrier between serum and clot after centrifugation
The polyethylene glycol gel migrates during centrifugation to form a physical barrier between the serum layer and the clot, preserving serum integrity.
Question 5: A 24-hour urine collection must be preserved with hydrochloric acid (HCl). Which test most commonly requires this preservative?
- Urine culture and sensitivity
- Urine catecholamines or metanephrines (Correct answer)
- Urinalysis with microscopy
- Urine pregnancy test (hCG)
Correct answer: Urine catecholamines or metanephrines
Acid preservatives like HCl are required for 24-hour catecholamine and metanephrine collections to prevent oxidative breakdown of these compounds.
Question 6: When a requisition shows 'QNS,' what does this mean and what action is taken?
- Quantity not sufficient — the specimen volume is inadequate and the test cannot be performed; recollection is required (Correct answer)
- Quality not satisfactory — the specimen is hemolyzed and must be retested
- Quick notification sent — results are telephoned to the provider
- Queue not started — the specimen is pending centrifugation
Correct answer: Quantity not sufficient — the specimen volume is inadequate and the test cannot be performed; recollection is required
QNS (quantity not sufficient) means there is not enough specimen to run the requested test, requiring a new collection from the patient.
Question 7: Plasma specimens differ from serum specimens because plasma:
- Contains no red blood cells
- Retains clotting factors that have been removed from serum (Correct answer)
- Has a lower concentration of all electrolytes
- Is always collected in a red-top tube
Correct answer: Retains clotting factors that have been removed from serum
Plasma is obtained from anticoagulated blood and retains fibrinogen and other clotting factors, whereas serum is the liquid that remains after blood has clotted and those factors are consumed.
Phlebotomy Test Specimen Processing and Handling 3
Which of the following best describes the correct technique for mixing an EDTA tube after venipuncture?