Challenge Your Exam Readiness With Our Free Phlebotomy Practice Questions

Coagulation testing requires a precise 9:1 blood-to-anticoagulant ratio. Underfilling a light-blue tube leaves excess citrate, chelating too much calcium during testing and falsely prolonging clot-based assays (e.g., PT/INR, aPTT). With butterfly sets, the tubing contains air; if the light-blue tube is attached first, the initial vacuum can be partly consumed by the dead space, leading to underfill. The correct workaround is to use a non-additive discard tube first to fill the tubing, then attach the citrate tube to achieve proper volume. Therefore, underfilled citrate specimens should be rejected and recollected using this technique. Adding blood from another tube (Option B) contaminates the specimen with additives (e.g., EDTA), invalidating results. Extended centrifugation (Option D) does not correct the ratio error. Accepting an underfilled tube (Option A) compromises patient care because dosage decisions for anticoagulants or factor replacement rely on accurate coagulation times. Following collection device-specific steps and verifying fill lines protect analytical validity and align with exam expectations.