NHA Certified Phlebotomy Technician (CPT)Specimen HandlingEasy
A phlebotomy technician is preparing to process a potassium specimen collected in a lavender-top (EDTA) tube. Which of the following is crucial to prevent erroneous results?
- ACentrifuge the specimen within 30 minutes of collection.
- BStore the specimen at 37°C until processing.
- CMix the tube thoroughly by inverting 8-10 times immediately after collection.
- DProtect the specimen from light during transport.
Show answer & explanationAnswer & explanation
Correct answer: C. Mix the tube thoroughly by inverting 8-10 times immediately after collection.
EDTA tubes contain an anticoagulant that must be thoroughly mixed with the blood to prevent clotting. Insufficient mixing will lead to microclots, which can consume platelets and affect cell counts, or cause erroneous results in other tests if serum/plasma is drawn off clotted blood.
Why the other options are wrong
- A. While timely centrifugation is important for some tests, the immediate and most critical step for an EDTA tube is proper mixing.
- B. Storing at 37°C is inappropriate for most blood specimens and can degrade analytes and promote hemolysis.
- D. Light protection is for specific analytes (e.g., bilirubin), not generally for potassium in an EDTA tube.
EDTA Tube Mixing
EDTA tubes must be gently inverted 8-10 times immediately after collection to ensure proper mixing of the anticoagulant with the blood, preventing clot formation.
- Crucial for preventing microclots.
- Ensures accurate hematology results.
- Gently invert, do not shake.
Memory trick: EDTA: Every Drop Thoroughly Agitated.