Backward linear regression analysis was used to identify genetic and clinical factors contributing to warfarin dose requirements using log daily dose as a dependent variable and patients’ age, gender, smoking status, hypertension, diabetes, myocardial infarction, heart failure, hypothyroidism, renal impairment, beta-blockers, antiplatelet, CYP2C9, VKORC1, and CYP4F2 as independent variables (Table 5). The gene discussed is CYP2C9; the disease is heart failure.