NHA Certified Phlebotomy Technician (CPT)Collection RoutineMedium
A phlebotomy technician is performing a dermal puncture on an adult patient. After making the puncture, the technician should wipe away the first drop of blood. What is the reason for this action?
- ATo allow the appropriate amount of blood to accumulate for collection.
- BTo avoid clotting of the first drop in the collection device.
- CTo remove tissue fluid that could alter test results.
- DTo prevent contamination of the specimen with excess antiseptic.
Show answer & explanationAnswer & explanation
Correct answer: C. To remove tissue fluid that could alter test results.
The first drop of blood from a dermal puncture often contains tissue fluid (interstitial fluid) mixed with blood. This fluid can dilute the specimen and interfere with accurate test results, particularly for analytes like glucose and potassium. Wiping it away ensures a purer blood sample.
Why the other options are wrong
- A. Wiping away the first drop is not to accumulate blood, but to ensure quality.
- B. Clotting is prevented by proper mixing with anticoagulant; the first drop's issue is dilution.
- D. While possible, antiseptics should be dry before puncture; the primary concern is tissue fluid.
Wiping First Drop (Dermal Puncture)
The practice of discarding the initial drop of blood produced during a dermal (capillary) puncture before collecting the specimen, done to eliminate tissue fluid contamination.
- Tissue fluid can dilute the sample and affect test results.
- Ensures a more accurate and pure blood specimen.
- Especially important for glucose, potassium, and calcium tests.
- The second drop is typically used for collection.
Memory trick: WIPE First: Wipe, Impurity, Pure, Eliminate.