What lab test is essential for monitoring patients on heparin therapy?

Activated Partial Thromboplastin Time (APTT) is the essential lab test for monitoring patients on heparin therapy. Heparin is an anticoagulant used to prevent and treat thromboembolic disorders, and it works by inhibiting certain factors in the coagulation cascade, particularly those that are activated in the intrinsic pathway.

APTT specifically measures the efficiency and functionality of the intrinsic and common pathways of coagulation, which directly reflects the effectiveness of heparin therapy. APTT is prolonged when heparin is present, and this test helps ensure that the patient remains within the therapeutic range, allowing for effective anticoagulation without an increased risk of bleeding.

Other tests listed, while useful in certain contexts, do not provide the necessary information for managing heparin doses accurately. Prothrombin time (PT) primarily assesses the extrinsic pathway and is more relevant for monitoring vitamin K antagonists like warfarin. A complete blood count (CBC) gives an overview of blood cells but does not specifically address clotting factors. Liver function tests (LFTs) assess liver health but also do not measure coagulation specifically. Therefore, APTT is the vital test for those undergoing heparin therapy, as