Challenge Your Exam Readiness With Our Free Phlebotomy Practice Questions

Serum tubes require complete clot formation prior to centrifugation to prevent fibrin strands and microclots that can clog analyzers and distort results. For patients on anticoagulants or with delayed clotting, waiting the full clot time (~30 minutes for SST) is necessary unless your laboratory has validated a rapid thrombin tube (orange-top) for the ordered assays. Option B reflects these choices. Spinning before clot completion (Option A) yields fibrin contamination. Prolonged warming at 37 °C (Option C) is not standard and may alter analytes. “Pouring off” (Option D) is unsafe—never decant by pouring, as it risks aerosolization and contamination; use centrifugation and pipetting under proper conditions. When STAT urgency conflicts with clotting time, consult the lab/test catalog about a plasma alternative (e.g., lithium heparin) if clinically acceptable for the analyte. Matching matrix and handling to validated methods ensures accuracy and rapid, defensible turnaround.