Question

The anticoagulant effect of heparin is monitored using:

• A. INR
• B. aPTT
• C. PT
• D. Bleeding time

Hint:

Heparin → aPTT; Warfarin → PT/INR.

Answer 1

The Correct Option is B

Step 1: Understanding heparin and its mechanism
Heparin is a fast-acting anticoagulant that works by enhancing the activity of antithrombin III, which inhibits clotting factors IIa (thrombin) and Xa. It is commonly used in the prevention and treatment of deep vein thrombosis (DVT), pulmonary embolism (PE), and in cardiac procedures.

Step 2: Monitoring heparin therapy
The anticoagulant effect of unfractionated heparin is monitored using the activated partial thromboplastin time (aPTT). This test measures the efficiency of the intrinsic and common pathways of the coagulation cascade, which are affected by heparin.

Step 3: Target therapeutic range
The therapeutic range for aPTT in patients on heparin therapy is typically 1.5 to 2.5 times the normal control value. Monitoring ensures effective anticoagulation while minimizing the risk of bleeding.

Step 4: Why other options are incorrect

• INR: Primarily used to monitor warfarin therapy, not heparin.
• PT: Also used for warfarin monitoring; assesses the extrinsic pathway, not significantly affected by heparin.
• Bleeding time: Assesses platelet function and is not useful for monitoring anticoagulant drugs like heparin.

Step 5: Clinical importance
Regular monitoring of aPTT helps adjust the heparin dose to maintain optimal anticoagulation, preventing both clot formation and excessive bleeding.

aPTT = Standard test for monitoring unfractionated heparin therapy