What laboratory value indicates a therapeutic level for heparin?

The activated partial thromboplastin time (aPTT) is the laboratory value that indicates a therapeutic level for heparin. Heparin is an anticoagulant medication commonly used to prevent and treat thromboembolic disorders. Monitoring the aPTT is crucial in patients receiving heparin therapy because it measures the efficacy of the intrinsic pathway of coagulation, which is where heparin exerts its action.

When a patient is on heparin, the aPTT should be measured regularly to ensure that it is within a specific therapeutic range. This range is generally approximately 1.5 to 2.5 times the normal control value depending on the protocol used. If the aPTT is too short, it might indicate that the heparin dose is insufficient and could result in inadequate anticoagulation. Conversely, if the aPTT is too long, it could increase the risk of bleeding complications.

The other choices do not directly relate to heparin therapy. The International Normalized Ratio (INR) is primarily used to monitor warfarin therapy. The Partial Thromboplastin Time (PT) is used to assess the extrinsic pathway and is not the primary test for heparin monitoring. A