Which tube is used to check coagulation factors?

The blue top tube is specifically designed for coagulation studies due to its sodium citrate additive, which acts as an anticoagulant. This means that it prevents blood from clotting, which is essential when analyzing coagulation factors such as prothrombin time (PT) and activated partial thromboplastin time (aPTT). These tests require a precise measurement of the blood’s ability to clot, and the blue top tube ensures that the properties of the blood sample remain unchanged during transport and analysis.

The red top tube does not contain any additives, allowing the blood to clot, which makes it unsuitable for coagulation tests. The purple top tube typically contains EDTA, an anticoagulant used mainly for complete blood counts (CBC) and other hematology tests rather than coagulation profiles. The gray top tube usually contains additives like sodium fluoride and oxalate or EDTA, mainly used for glucose testing and lactate levels, not for coagulation factor assessments.