American Society Of Hematology (ASH) ITE Practice Test

Warfarin is used for long-term oral anticoagulation in patients who have a high risk of thrombosis from either prosthetic material or autoimmune thrombophilia. The two classic first-line indications are mechanical heart valves and antiphospholipid syndrome with a history of thrombosis. Mechanical heart valves create a surface that readily promotes clot formation, so lifelong anticoagulation with warfarin is essential to prevent valve thrombosis and systemic embolism, with target INR requirements that vary by valve type and position. In antiphospholipid syndrome, especially after a thrombotic event, long-term warfarin reduces the risk of recurrent thrombosis more reliably than alternatives in many cases, guiding ongoing therapy with a therapeutic INR. In contrast, warfarin is avoided in pregnancy due to teratogenicity, and while DVT and atrial fibrillation are common indications for anticoagulation, the two strongest and most definitive scenarios for warfarin use are mechanical valves and antiphospholipid–related thrombosis.