Which tube is used primarily for coagulation tests?

The light blue tube is specifically designed for coagulation tests due to the presence of sodium citrate as an additive. Sodium citrate acts as an anticoagulant, binding calcium in the blood and preventing it from clotting during the testing process. This preservation of the sample in a non-clotted state is crucial for accurate coagulation test results, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT). In contrast, other tubes, such as the gold, red, and purple tubes, contain different additives or lack anticoagulants, making them unsuitable for precise coagulation testing. The light blue tube is therefore optimal for evaluating the blood's clotting ability, ensuring that tests conducted yield reliable data for clinical decision-making.