A 48-year-old woman is found to have markedly elevated LDL cholesterol (220 mg/dL) and total cholesterol (320 mg/dL) on routine screening. Her triglycerides are 95 mg/dL and HDL-C is 52 mg/dL. She has no personal history of cardiovascular disease but her father died of myocardial infarction at age 55. Physical examination reveals tendon xanthomas on the Achilles tendons and corneal arcus. What is the most appropriate next step?