For a complete blood count and measurement of prothrombin time, are lavender stopper and green stopper tubes acceptable specimens?

The correct response is that citrate is necessary for coagulation testing. Prothrombin time (PT) is a specific test that evaluates the extrinsic and common pathways of coagulation, and it requires citrate as an anticoagulant for accurate results. When using a tube with a lavender stopper, typically containing EDTA as the anticoagulant, it can interfere with coagulation tests, including PT, because EDTA binds calcium, which is crucial for the clotting process.

Additionally, green stopper tubes, which generally use heparin as an anticoagulant, are also unsuitable for PT measurement for similar reasons. Heparin can alter the normal coagulation pathways being measured, thus affecting the accuracy of the prothrombin time results. Therefore, the use of citrate (usually found in light blue stopper tubes) is essential for performing reliable prothrombin time tests. This emphasis on using the correct type of anticoagulant ensures that hematological results are valid and clinically useful.