What type of additive is found in the light blue top tube?

The light blue top tube contains sodium citrate as its additive, which plays a crucial role in blood coagulation studies. Sodium citrate works as an anticoagulant by binding to calcium ions in the blood. Calcium is essential for the coagulation cascade; thus, by chelating these ions, sodium citrate effectively prevents the blood from clotting in the tube. This property makes the light blue tube particularly useful for tests that measure coagulation parameters, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT).

Understanding the function of additives in different collection tubes is essential for accurate test results. In contrast, heparin, EDTA, and silica gel serve different purposes. Heparin, which is typically found in green top tubes, acts as an anticoagulant but through a different mechanism. EDTA, found in lavender or purple top tubes, is another anticoagulant that binds calcium; however, it is commonly used for hematology tests rather than coagulation studies. Silica gel, found in some serum separator tubes, promotes clot formation and is not suitable for coagulation tests. Therefore, recognizing that sodium citrate is the additive specific to the light blue top tube is critical for proper specimen collection and