From the Guidelines
The primary lab tests for diagnosing rhabdomyolysis are serum creatine kinase (CK) or creatine phosphokinase (CPK), myoglobin, and plasma creatinine, with CK levels above 5 times normal (approximately 1000 IU/L) being a sign of rhabdomyolysis 1. When evaluating patients for rhabdomyolysis, it is essential to consider the following lab tests:
- Serum creatine kinase (CK) or creatine phosphokinase (CPK) to assess muscle damage
- Myoglobin in both blood and urine to identify the risk of acute kidney injury, which is correlated with increased mortality 1
- Plasma creatinine to assess kidney function
- Electrolytes, particularly potassium, to monitor for hyperkalemia
- Complete metabolic panel to evaluate kidney function, electrolytes, and liver function
- Urinalysis with dipstick to detect myoglobinuria, which may appear as tea or cola-colored urine
- Complete blood count to identify potential infection or inflammation contributing to muscle breakdown These tests are crucial in diagnosing rhabdomyolysis and guiding prompt treatment to prevent complications such as acute kidney injury, electrolyte imbalances, and compartment syndrome 1.
From the Research
Lab Tests for Rhabdomyolysis
The following lab tests are used to diagnose and monitor rhabdomyolysis:
- Serum creatine kinase (CK) level: a key marker for muscle damage, with levels > 1000 U/L or at least 5x the upper limit of normal indicating rhabdomyolysis 2, 3, 4
- Serum myoglobin level: elevated in rhabdomyolysis, with a myoglobin/CK ratio > 0.2 associated with an increased likelihood of developing acute kidney injury (AKI) 5
- Urinalysis: to check for myoglobinuria, which can indicate rhabdomyolysis 2, 6
- Full metabolic panel: including serum creatinine and electrolytes to assess renal function and electrolyte imbalances 2
- McMahon score: a predictive tool for AKI requiring renal replacement therapy, with a score of 6 or greater indicating high risk 2, 3
Additional Diagnostic Tools
Other diagnostic tools that may be used to evaluate rhabdomyolysis include:
- Muscle biopsy: to assess muscle damage and differentiate between acquired and inherited causes of rhabdomyolysis 6
- Genetic testing: to identify inherited disorders that may predispose to rhabdomyolysis, such as glycogen metabolism disorders or mitochondrial oxidative phosphorylation disorders 6
- Clinical examination and history: to identify underlying causes of rhabdomyolysis, such as substance abuse, medication or toxic exposures, or autoimmune myopathies 6