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) Low density lipoprotein (LDL): Atorvastatin is primarily prescribed to lower LDL cholesterol levels, which are directly associated with an increased risk of coronary artery disease. A decrease in LDL levels indicates that the medication is effectively managing the client’s cholesterol levels and reducing the risk of cardiovascular events. B) High density lipoprotein (HDL): While higher levels of HDL cholesterol are generally considered protective against heart disease, atorvastatin’s main purpose is to lower LDL levels. Therefore, an increase in HDL does not necessarily indicate that the atorvastatin is achieving its primary therapeutic effect in reducing cardiovascular risk. C) Creatine phosphokinase (CK): This enzyme level is monitored primarily to assess muscle damage and the potential side effects of statins like atorvastatin, such as rhabdomyolysis. While elevated CK levels can indicate muscle issues, they do not provide direct information about the effectiveness of atorvastatin in managing cholesterol levels or coronary artery disease risk. D) Prothrombin time (PT): PT is a measure of blood coagulation and is not relevant to the effectiveness of atorvastatin. While important for monitoring anticoagulation therapy, PT does not provide insight into lipid levels or the impact of atorvastatin on coronary artery disease risk. Thus, it is not an appropriate indicator of the medication's desired effects.