An increase in which serum laboratory value indicates to the nurse that a prescription for atorvastatin is having the desired effect for a client at risk for coronary artery disease?

A. High-density lipoprotein (HDL): HDL helps transport cholesterol from the arteries to the liver for excretion, offering a protective effect against coronary artery disease. An increase in HDL indicates improved lipid profile and reflects the desired therapeutic outcome of atorvastatin therapy. B. Prothrombin time (PT): PT measures clotting ability and is not directly affected by atorvastatin. This test is more relevant for clients on anticoagulants such as warfarin rather than lipid-lowering therapy. C. Low-density lipoprotein (LDL): Atorvastatin works to lower LDL, which contributes to plaque buildup in arteries. The desired effect would be a decrease, not an increase, in LDL levels, so rising LDL would suggest treatment failure. D. Creatine phosphokinase (CK): CK is an enzyme that increases with muscle injury, including the rare but serious side effect of statin-induced myopathy. Monitoring CK helps detect adverse effects, but an increase is not a desired outcome.