American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

Which specimen should be collected last during a skin puncture procedure?

1. EDTA micro collection tubes

2. Heparin micro collection tubes

3. Sodium citrate micro collection tubes

4. Serum micro collection tubes

The correct answer is: Heparin micro collection tubes

In a skin puncture procedure, the order of specimen collection is crucial to prevent contamination and ensure the accuracy of the test results. When collecting specimens, it is important to consider the tube additives and their potential effects on subsequent samples. The correct choice specifies that serum micro collection tubes should be collected last. This is because serum collection tubes contain no anticoagulants, which means they rely on the formation of a clot to separate the serum from the cells. When blood is drawn from a puncture, the initial samples collected often contain higher concentrations of certain substances, including potential anticoagulants from other tubes. If serum tubes are collected first, any contamination from anticoagulant-containing tubes could alter the serum results. By collecting the serum micro collection tubes last, you minimize the risk of contamination from any additives present in the earlier collected tubes, ensuring that the serum sample is as pure and accurate as possible. This practice adheres to the standard procedures for phlebotomy and specimen collection, which helps in maintaining the integrity of each sample for reliable test results.