What laboratory test is primarily used for diagnosing rhabdomyolysis?

The primary laboratory test used for diagnosing rhabdomyolysis is the measurement of creatine kinase (CK) levels. Rhabdomyolysis involves the breakdown of muscle tissue, which releases various intracellular components into the bloodstream. Creatine kinase is an enzyme found in high concentrations in skeletal muscle, and its release into the blood significantly increases in the event of muscle injury or damage.

A markedly elevated level of creatine kinase, particularly when it is more than five times the normal range, typically indicates rhabdomyolysis. This increase often correlates with muscle damage and helps establish the diagnosis. While myoglobin can also be relevant in the context of muscle injury, creatine kinase levels provide a more specific and reliable indication of muscle breakdown, helping to distinguish rhabdomyolysis from other conditions.

Other tests, such as troponin and lactate dehydrogenase, have different clinical implications and are not primary indicators of rhabdomyolysis. Troponin, for example, is primarily used to assess cardiac muscle injury. Therefore, creatine kinase is the most appropriate laboratory test for diagnosing rhabdomyolysis.