CMLA Specimen Collection & Handling 5 — Questions and Answers
Question 1: A specimen requires centrifugation to obtain serum. Which tube type must be allowed to clot completely before centrifugation?
- EDTA (lavender-top)
- Sodium citrate (light blue)
- SST/serum separator tube (gold-top) (Correct answer)
- Sodium heparin (green-top)
Correct answer: SST/serum separator tube (gold-top)
SST tubes contain a clot activator and gel separator; the tube must be allowed to clot completely (usually 30 minutes) before centrifugation to obtain quality serum.
Question 2: A patient refuses to have blood drawn. What is the appropriate response?
- Proceed quickly before the patient changes their mind
- Document the refusal, inform the nurse or provider, and do not collect the specimen (Correct answer)
- Ask a family member to convince the patient
- Collect the specimen with minimal explanation to reduce anxiety
Correct answer: Document the refusal, inform the nurse or provider, and do not collect the specimen
Competent patients have the right to refuse procedures; the refusal should be documented and the ordering provider notified so alternative plans can be made.
Question 3: Which of the following analytes is most affected by prolonged exposure of a blood specimen to light?
- Sodium
- Bilirubin (Correct answer)
- Creatinine
- Hemoglobin A1c
Correct answer: Bilirubin
Bilirubin is photosensitive and degrades rapidly when exposed to light; specimens for bilirubin testing should be protected with amber tubes or foil.
Question 4: A requisition calls for a 'trough' drug level. When should this specimen be collected?
- 30 minutes after drug administration
- Immediately before the next scheduled dose (Correct answer)
- 2 hours after drug administration
- At any convenient time during the dosing interval
Correct answer: Immediately before the next scheduled dose
Trough levels represent the lowest drug concentration in the blood and must be collected immediately before the next scheduled dose.
Question 5: Which PPE is required at minimum during routine venipuncture per standard precautions?
- Gloves only (Correct answer)
- Gloves and gown
- Gloves, gown, and face shield
- No PPE required for routine draws
Correct answer: Gloves only
Standard precautions require gloves as a minimum for all venipuncture procedures; additional PPE is added if splash or spray risk is anticipated.
Question 6: Potassium (K+) results are critically high on a sample with no hemolysis noted. The laboratory assistant should first:
- Report the result immediately to the physician
- Check the sample for clots and verify proper collection technique before reporting (Correct answer)
- Recollect the specimen before contacting anyone
- Assume the result is correct and document it
Correct answer: Check the sample for clots and verify proper collection technique before reporting
Before reporting a critical potassium value, verifying the specimen for clots or preanalytical errors ensures accurate results, since hyperkalemia can trigger dangerous clinical interventions.
Question 7: Which of the following statements is true regarding the use of a butterfly (winged infusion) set for venipuncture?
- It always produces better quality specimens than straight needles
- A discard tube should be drawn first when collecting coagulation tests to remove air from the tubing (Correct answer)
- It should never be used for pediatric patients
- It cannot be used with evacuated tube systems
Correct answer: A discard tube should be drawn first when collecting coagulation tests to remove air from the tubing
When using a butterfly set for coagulation testing, a discard tube is drawn first to fill the tubing dead space with blood and prevent air from diluting the sodium citrate ratio.
CMLA Specimen Collection & Handling 5
A specimen requires centrifugation to obtain serum.
Which tube type must be allowed to clot completely before centrifugation?