From the Guidelines
Laboratory tests for diagnosing and managing rhabdomyolysis should include serum creatine kinase (CK), serum creatinine, BUN, electrolytes, urinalysis, and urine myoglobin, as these tests allow clinicians to diagnose rhabdomyolysis, assess its severity, and monitor for complications like acute kidney injury and electrolyte abnormalities. The most recent and highest quality study, 1, recommends performing a repeated bio-assessment combining plasma myoglobin, plasma creatine phosphokinase (CPK), and kalaemia measurements to detect acute kidney injury in patients suffering from post-traumatic acute rhabdomyolysis. Key laboratory tests for rhabdomyolysis include:
- Serum creatine kinase (CK), which is the most important test and should be monitored serially as levels typically rise within 12 hours of muscle injury and peak at 24-72 hours
- Serum creatinine and BUN to assess kidney function
- Electrolytes (particularly potassium, calcium, and phosphorus) to monitor for life-threatening imbalances
- Urinalysis to check for myoglobinuria
- Urine myoglobin if available
- Complete blood count, liver function tests, and coagulation studies to evaluate for complications or underlying causes
- Arterial blood gases may be needed in severe cases to assess for metabolic acidosis, as suggested by 1. These tests should be performed at presentation and repeated at intervals based on clinical status, with CK levels monitored daily until declining, as recommended by the most recent study 1.
From the Research
Labs for Rhabdomyolysis Diagnosis and Management
The following labs are recommended for diagnosing and managing rhabdomyolysis:
- Serum creatine kinase (CK) level: diagnosis is confirmed when CK level is > 1000 U/L or at least 5x the upper limit of normal 2
- Serum myoglobin: important test to request, as myoglobinaemia may lead to toxin-induced tubular necrosis and impairment of renal function 2, 3
- Urinalysis: to check for myoglobinuria, which is a sign of muscle necrosis 2, 3
- Full metabolic panel: including serum creatinine and electrolytes, to monitor for electrolyte imbalances and acute kidney injury (AKI) 2
- A McMahon score: calculated on admission, to predict the risk of AKI requiring renal replacement therapy 2
Additional Labs and Considerations
Other labs and considerations that may be relevant in the diagnosis and management of rhabdomyolysis include:
- Liver function tests: as abnormal liver function tests are frequently observed in cases of severe rhabdomyolysis, although serum aminotransferases lack tissue specificity to distinguish primary liver injury from muscle injury 4
- Electrolyte panels: to monitor for electrolyte imbalances, such as hyperkalaemia and hypocalcaemia, which can be life-threatening 3
- Renal function tests: to monitor for AKI, which is a common complication of rhabdomyolysis 2, 3, 5