What is contained in the blue stoppered tube?

The blue stoppered tube is commonly used for coagulation testing and contains sodium citrate, which acts as an anticoagulant. This anticoagulant works by binding calcium ions in the blood, which are essential for the coagulation process. Therefore, when blood is drawn into a blue top tube, the resulting specimen is plasma, not serum.

Plasma is the liquid component of blood that remains after the blood has been prevented from clotting, allowing you to analyze various components like clotting factors, proteins, and other substances. In contrast, serum, which is commonly collected in a red-top or serum separator tube, is the fluid that remains after the blood has clotted and the clot has been removed.

This distinction is crucial as different tests require either plasma or serum, depending on what is being measured. Hence, the blue stoppered tube specifically provides plasma for analyses related to coagulation.