The nurse is reviewing the client's laboratory values. 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): While HDL levels are important for assessing cardiovascular risk, atorvastatin primarily targets the reduction of low-density lipoprotein (LDL) cholesterol. An increase in HDL is generally beneficial, but it is not the primary measure of atorvastatin's effectiveness. B. Prothrombin time (PT): PT measures blood clotting ability and is not directly related to the effectiveness of atorvastatin. Atorvastatin’s role is to manage cholesterol levels, not to influence coagulation directly. C. Creatine phosphokinase (CK): CK levels can be monitored to assess muscle damage or myopathy, a potential side effect of atorvastatin. However, changes in CK are not a direct measure of the medication’s effectiveness in lowering cholesterol. D. Low-density lipoprotein (LDL): This is the most appropriate indicator of atorvastatin's effectiveness. Atorvastatin is a statin medication used to lower LDL cholesterol levels, which is a primary goal in managing and reducing the risk of coronary artery disease. A decrease in LDL cholesterol levels reflects that the medication is working as intended.