Which lab test is primarily monitored for patients on heparin?

The activated partial thromboplastin time (aPTT) is the primary laboratory test used to monitor patients on heparin therapy. Heparin is an anticoagulant that works by inhibiting several factors in the coagulation cascade, specifically factors XII, XI, IX, and X, resulting in a prolongation of the aPTT. This test evaluates the intrinsic and common pathways of coagulation, allowing healthcare providers to determine the effectiveness and safety of heparin dosing.

Monitoring aPTT helps to ensure that patients are within a therapeutic range that reduces the risk of thromboembolic events while minimizing the risk of bleeding complications. The aPTT is typically kept at a target range that is two to three times longer than the normal value, depending on the treatment goals.

Additionally, while other lab tests, such as the PT/INR, hemoglobin, and platelet count, provide useful information about a patient's overall health and other aspects of coagulation, they are not the primary tests used to assess the efficacy of heparin therapy. The PT/INR is principally used for monitoring warfarin therapy, the hemoglobin level is crucial for assessing anemia or evaluating blood loss, and platelet counts are essential for screening for thromb