Which tube is primarily used for coagulation studies in the order of draw?

The light blue tube is specifically designed for coagulation studies due to its additive, which is sodium citrate. This anticoagulant works by binding calcium in the blood, thereby preventing clot formation. This characteristic allows for accurate measurement of coagulation parameters, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT).

In the context of the order of draw, the light blue tube is positioned early in the sequence to avoid contamination from the additives found in other tubes. This is crucial for ensuring that the coagulation studies reflect the blood's true clotting ability without interference from other substances.

The other tubes mentioned serve different purposes; for instance, the gold, tiger, or marble tubes often contain a gel separator and are used for serum tests, the dark green tube contains heparin for plasma chemistry tests, and the pink tube is designated for blood banking. Each of these has distinct applications that do not align with coagulation studies like the light blue tube does.