What tube is commonly used for coagulation tests?

The light blue tube is specifically designed for coagulation tests because it contains sodium citrate as an anticoagulant. This anticoagulant is essential for preserving the blood’s ability to clot and is used in tests like prothrombin time (PT) and partial thromboplastin time (PTT). Sodium citrate works by binding calcium ions in the blood; since calcium is crucial for the clotting process, its removal ensures that the sample can be evaluated for clotting ability without interference from coagulation processes.

The other tubes serve different purposes: the red top tube is often used for serum tests and does not contain any anticoagulants, which is unsuitable for coagulation studies. The green top tube is used for tests requiring heparin, another type of anticoagulant but primarily for different tests such as chemistry profiles. The lavender top tube contains EDTA, which is used mainly for complete blood counts and other hematological tests but is not ideal for coagulation studies where the measurement of clotting time is required.