What color tube is used before performing a Prothrombin Time test?

The light blue top tube is used before performing a Prothrombin Time (PT) test because it contains sodium citrate, an anticoagulant that binds calcium in the blood sample. This anticoagulant is crucial for obtaining accurate coagulation test results, as it prevents the blood from clotting before the test is performed. The PT test measures how long it takes for blood to clot, which is essential for assessing the coagulation pathway and monitoring patients on anticoagulant therapy.

Each color tube serves a specific purpose based on its additive. For instance, the lavender top tube contains EDTA, which is primarily used for hematology tests. The gold top tube typically contains a serum separator gel and a clot activator, which is not appropriate for tests requiring an anticoagulant. The red top tube does not contain any additives and is generally used for serum tests, making it unsuitable for PT testing where blood must remain in a non-clotted state until analyzed.