From the Guidelines
For a patient suspected of having rhabdomyolysis, the essential laboratory tests to order include serum creatine kinase (CK), serum creatinine, plasma potassium, and myoglobin levels. These tests are crucial in diagnosing and managing rhabdomyolysis, as they help assess the extent of muscle breakdown and kidney function 1.
Key Laboratory Tests
- Serum creatine kinase (CK): elevated levels, typically at least 5 times the upper limit of normal, indicate muscle breakdown 1
- Serum creatinine: assesses kidney function and helps identify potential acute kidney injury 1
- Plasma potassium: checks for hyperkalemia, a common complication of rhabdomyolysis 1
- Myoglobin levels: may be more sensitive and specific than CK in identifying the risk of acute kidney injury 1 Additional tests, such as electrolyte panels, complete blood count (CBC), urinalysis, liver function tests, and coagulation studies, may also be necessary to evaluate for other complications and guide management.
Rationale for Test Selection
The selection of these laboratory tests is based on the latest evidence, which highlights the importance of early diagnosis and management of rhabdomyolysis to prevent life-threatening complications, including renal failure and electrolyte abnormalities 1. By ordering these essential laboratory tests, healthcare providers can promptly identify patients at risk and initiate aggressive IV fluid resuscitation and other necessary interventions to improve outcomes.
From the Research
Laboratory Tests for Rhabdomyolysis
To diagnose and manage rhabdomyolysis, several laboratory tests should be ordered, including:
- Serum creatine kinase (CK) level: a level > 1000 U/L or at least 5x the upper limit of normal is diagnostic of rhabdomyolysis 2
- Serum myoglobin: to check for myoglobinuria, which can cause acute kidney injury (AKI) 2
- Urinalysis: to check for myoglobinuria and other abnormalities 2
- Full metabolic panel: including serum creatinine and electrolytes to evaluate renal function and electrolyte imbalances 2
- Blood urea nitrogen (BUN) and creatinine levels: to assess renal function, although the BUN/creatinine ratio may not be a reliable indicator of renal function in rhabdomyolysis 3
Additional Considerations
In some cases, rhabdomyolysis may occur with normal CK levels, and other diagnostic markers such as myoglobin casts in the urine may be useful 4. The A McMahon score, calculated on admission, can predict the risk of AKI requiring renal replacement therapy 2.
Laboratory Tests to Monitor Progression and Complications
Regular monitoring of laboratory tests, including CK, myoglobin, and renal function tests, is essential to assess the progression of rhabdomyolysis and the development of complications such as AKI 5, 6. Electrolyte imbalances and other complications should also be monitored and managed promptly 2, 6.