NHA Certified Phlebotomy Technician (CPT)Specimen HandlingMedium
A phlebotomy technician is processing a specimen for a glucose tolerance test (GTT). Which of the following is the most appropriate action for the collected blood samples?
- AFreeze the whole blood samples immediately after collection.
- BStore all samples at room temperature for up to 8 hours.
- CProtect the samples from light to prevent degradation.
- DCentrifuge the samples and separate plasma within 60 minutes.
Show answer & explanationAnswer & explanation
Correct answer: D. Centrifuge the samples and separate plasma within 60 minutes.
For GTT samples, glucose in whole blood is rapidly consumed by red blood cells. To prevent falsely low glucose results, plasma or serum must be separated from the cells within a short timeframe (typically 30-60 minutes) or collected in a tube containing a glycolysis inhibitor like sodium fluoride.
Why the other options are wrong
- A. Freezing whole blood can cause hemolysis and is generally not recommended for routine glucose analysis; plasma/serum is frozen if long-term storage is needed.
- B. Storing whole blood at room temperature for extended periods allows glycolysis to continue, leading to decreased glucose levels.
- C. Light protection is not typically a requirement for glucose samples.
Glucose Specimen Processing
Blood specimens for glucose testing, especially GTT, require prompt separation of plasma/serum from cells or collection in tubes with glycolysis inhibitors to prevent glucose consumption by red blood cells.
- Glucose decreases in whole blood over time.
- Separate plasma/serum within 30-60 minutes.
- Sodium fluoride tubes inhibit glycolysis.
Memory trick: Glucose Gone Quickly: Separate or Stop.