Which color tube is commonly used to collect blood for plasma?

The green tube is used for collecting blood for plasma because it contains heparin, an anticoagulant that prevents the blood from clotting. This property allows the collected blood to remain in a liquid state, making it suitable for plasma analysis. When blood is drawn into a green top tube, the heparin binds to the thrombin, effectively halting the coagulation process, which is essential when plasma is the desired specimen for diagnostic testing.

In contrast, red tubes are typically used for serum collection since they do not contain any anticoagulants and allow the blood to clot, thereby separating serum from the cellular components after centrifugation. The purple tube often contains EDTA, which is also an anticoagulant, but it is primarily used for whole blood tests and not specifically for plasma. The gray tube contains additives such as glycolytic inhibitors, which are mainly used for specific testing like glucose levels rather than routine plasma collection. Thus, the green tube is the correct choice for collecting blood intended for plasma analysis.