Which biomarker is typically used to diagnose rhabdomyolysis?

• A. C-reactive protein
• B. Lactate dehydrogenase
• C. Creatine kinase (CK/CPK)
• D. Troponin

Answer: (C)

Creatine kinase is the primary indicator used when diagnosing rhabdomyolysis because it is highly concentrated in skeletal muscle and is released in large amounts when muscle fibers are damaged. This makes CK a sensitive, muscle-specific marker for muscle injury, so markedly elevated CK levels reliably point to rhabdomyolysis and help gauge the extent of damage and potential risk for kidney complications. In contrast, C-reactive protein is a general inflammatory marker and does not indicate muscle injury specifically; lactate dehydrogenase is non-specific and can rise in many conditions; troponin is specific to cardiac muscle injury, not skeletal muscle. CK levels begin to rise within hours of injury and can climb into very high values, peaking days later, which is why it’s the go-to diagnostic biomarker for rhabdomyolysis.