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

What is the recommended minimum time for allowing blood to clot in a serum separator tube?

1. 15 minutes

2. 30 minutes

3. 60 minutes

4. 45 minutes

The correct answer is: 30 minutes

The recommended minimum time for allowing blood to clot in a serum separator tube is 30 minutes. This period is essential because it allows sufficient time for the blood to coagulate fully, ensuring that the serum can be separated effectively during centrifugation. The clotting process involves the activation of clotting factors and the aggregation of platelets, which collectively form a stable clot. If the blood is centrifuged before it has adequately clotted, serum may not be separated from the cellular components effectively, leading to potential inaccuracies in test results. Choosing a time shorter than 30 minutes may result in an incomplete clot, potentially causing hemolysis or contamination of the serum with cellular elements. Conversely, waiting significantly longer than 30 minutes might not necessarily improve the quality of serum obtained, but may instead contribute to changes in biochemical constituents due to prolonged contact between serum and cellular components or delays in processing.