Step 3 UWSA Practice Exam

When starting warfarin in atrial fibrillation, you need to establish the patient’s baseline coagulation status and organ function because warfarin’s effect depends on hepatic metabolism and vitamin K–dependent clotting. A CBC checks for thrombocytopenia or existing anemia that could raise bleeding risk. Kidney and liver function are important because warfarin is processed mainly by the liver, and liver disease can increase bleeding risk and alter metabolism; kidney function helps gauge overall health and potential medication interactions. A baseline INR is essential to know where the patient stands before therapy and to guide future dose adjustments and monitoring. Also, assessing potential drug interactions and overall bleeding risk informs safe initiation and management of therapy. Lipid panel, electrolyte panel, and thyroid function aren’t required specifically to start warfarin, though they may be relevant for broader AF care.