Which color tube is generally used for coagulation studies and contains sodium citrate?

The light blue tube is specifically designed for coagulation studies and contains sodium citrate as its additive. Sodium citrate acts as an anticoagulant by binding calcium in the blood, which is crucial for accurate clotting tests. These tests, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT), require precise control of coagulation factors, and the use of sodium citrate helps to achieve this by preventing clot formation during the collection and processing of the sample.

In contrast, the other colored tubes serve different purposes. The green tube, for example, typically contains heparin, which is suitable for tests requiring plasma but not specifically for coagulation studies. The gray tube is used for glucose testing and contains an additive to preserve glucose levels. The lavender tube is used for hematology tests and contains EDTA, which also acts as an anticoagulant but is not ideal for coagulation studies due to its potential to interfere with some of the clotting factors. Thus, the light blue tube is the correct choice for coagulation testing due to its specific composition and purpose.