What type of test requires a light blue top tube?

The light blue top tube is specifically used for coagulation tests, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT). This tube contains sodium citrate as an anticoagulant, which helps to prevent the blood from clotting. The anticoagulant works by binding calcium ions in the blood, which are necessary for the clotting process. Therefore, it is essential to use this particular tube for tests that measure the blood's ability to clot, ensuring accurate results.

Tests such as HIV testing, complete blood counts, and thyroid function tests typically require different types of tubes equipped with different additives to provide the appropriate environment for the laboratory analyses performed.