What is a blue top tube primarily used for?

A blue top tube is primarily used for coagulation studies due to its specific additive, which is sodium citrate. This anticoagulant works by binding calcium ions in the blood, thereby preventing clot formation. Coagulation tests, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT), are essential for assessing the blood's ability to clot and for monitoring patients on anticoagulant therapy.

The other options do not apply to the blue top tube: chemistry analysis typically requires a green or red top tube, glucose testing is usually done using a gray top tube due to its sodium fluoride additive, and hematology tests generally utilize lavender top tubes, which contain EDTA as an anticoagulant. Each tube's color signifies specific additives that are suitable for different types of testing, ensuring accurate and effective results.