A patient with signs of proximal muscle weakness and tenderness who started a statin six months ago should have which test performed?

• A. Urinalysis
• B. Liver function tests
• C. Creatine kinase levels
• D. Serum lipids

Answer: (C)

Statin-associated myopathy can present with proximal muscle weakness and tenderness, so the most informative test is measurement of creatine kinase levels. CK is an enzyme released from damaged muscle, and its elevation directly reflects muscle injury from statins. The higher the CK, the more likely there is significant muscle damage, with very high levels suggesting rhabdomyolysis and requiring urgent attention.

Liver function tests assess hepatotoxicity, which is a different adverse effect and not the cause of this presentation. Serum lipids measure cholesterol levels and do not indicate muscle injury. Urinalysis isn’t the primary diagnostic test for statin myopathy, though it becomes relevant if rhabdomyolysis is suspected to look for myoglobinuria. The key step here is checking CK to confirm muscle injury from the statin.