CLC CLC Specimen Collection, Handling & Pre-Analytical Processes 1 — Questions and Answers
Question 1: The pre-analytical phase of laboratory testing is considered the most error-prone phase. Which of the following is a common pre-analytical error?
- Incorrect calibration of instrument
- Hemolyzed specimen due to improper collection technique (Correct answer)
- Transcription error in result reporting
- Reagent lot-to-lot variation
Correct answer: Hemolyzed specimen due to improper collection technique
Hemolysis from improper venipuncture technique is one of the most frequent pre-analytical errors, which can falsely alter results for multiple analytes.
Question 2: According to CLSI guidelines, what is the recommended order of draw when collecting multiple tubes during a single venipuncture?
- EDTA → SST → citrate → heparin
- Blood culture → citrate → SST → heparin → EDTA (Correct answer)
- SST → EDTA → citrate → blood culture
- Heparin → EDTA → SST → citrate
Correct answer: Blood culture → citrate → SST → heparin → EDTA
CLSI GP41 specifies the order: blood cultures first, then citrate (blue), then SST or plain red, then heparin (green), then EDTA (lavender) to prevent cross-contamination between additives.
Question 3: A laboratory consultant reviews rejection criteria and notes that a urine specimen for culture arrived in the laboratory 4 hours after collection without refrigeration. What is the appropriate action?
- Process the specimen and note the delay
- Reject the specimen and request a new collection (Correct answer)
- Centrifuge immediately and process
- Add a preservative and proceed
Correct answer: Reject the specimen and request a new collection
Unrefrigerated urine held more than 2 hours before culture is typically rejected because bacterial overgrowth invalidates culture results.
Question 4: Which anticoagulant tube is the correct choice for a prothrombin time (PT/INR) test?
- EDTA (lavender top)
- Heparin (green top)
- Sodium citrate (blue top) (Correct answer)
- Serum separator tube (gold top)
Correct answer: Sodium citrate (blue top)
Sodium citrate (blue top) tubes are required for coagulation studies including PT/INR because citrate preserves clotting factors by chelating calcium.
Question 5: A phlebotomist collects a citrate tube but it is only 80% full. What is the most significant concern with this specimen?
- Insufficient volume for the analyzer
- Altered blood-to-anticoagulant ratio affecting coagulation results (Correct answer)
- Risk of clot formation in the tube
- Tube vacuum loss
Correct answer: Altered blood-to-anticoagulant ratio affecting coagulation results
Citrate tubes require a precise 9:1 blood-to-anticoagulant ratio; underfilling alters this ratio and leads to falsely prolonged coagulation results.
Question 6: Which specimen type is most appropriate for measuring ionized calcium?
- Serum (SST tube, spun)
- Whole blood collected in a heparinized syringe (Correct answer)
- Plasma from EDTA tube
- 24-hour urine collection
Correct answer: Whole blood collected in a heparinized syringe
Ionized calcium is best measured in heparinized whole blood collected anaerobically, as EDTA chelates calcium and serum requires careful handling to avoid pH changes.
CLC CLC Specimen Collection, Handling & Pre-Analytical Processes 1
The pre-analytical phase of laboratory testing is considered the most error-prone phase.
Which of the following is a common pre-analytical error?