Which laboratory test is used to monitor unfractionated heparin therapy?

Which laboratory test is used to monitor unfractionated heparin therapy?

• A. Glucose
• B. INR
• C. aPTT
• D. Creatinine

Answer: (C)

Unfractionated heparin therapy is monitored with the aPTT because it measures the effect of heparin on the intrinsic and common coagulation pathways via antithrombin. Heparin speeds up antithrombin’s inactivation of thrombin and Factor Xa, so the time it takes for blood to clot increases as the anticoagulant effect rises. Clinicians target a specific aPTT range (often 1.5–2.5 times the baseline or a protocol-defined range) to balance preventing clots with avoiding bleeding. Other labs serve different purposes: glucose monitors metabolic status, INR tracks warfarin therapy, and creatinine assesses kidney function. In some settings, an anti-Xa level can be used as an alternative monitoring method, but aPTT is the standard for unfractionated heparin.

Unfractionated heparin therapy is monitored with the aPTT because it measures the effect of heparin on the intrinsic and common coagulation pathways via antithrombin. Heparin speeds up antithrombin’s inactivation of thrombin and Factor Xa, so the time it takes for blood to clot increases as the anticoagulant effect rises. Clinicians target a specific aPTT range (often 1.5–2.5 times the baseline or a protocol-defined range) to balance preventing clots with avoiding bleeding. Other labs serve different purposes: glucose monitors metabolic status, INR tracks warfarin therapy, and creatinine assesses kidney function. In some settings, an anti-Xa level can be used as an alternative monitoring method, but aPTT is the standard for unfractionated heparin.