From the Guidelines
Rhabdomyolysis diagnosis is primarily based on laboratory tests, including creatine kinase (CK) levels, which should be elevated at least 5 times above the upper limit of normal, as well as myoglobin, plasma potassium, and creatinine tests 1. The diagnosis of rhabdomyolysis involves a combination of clinical presentation and laboratory findings. Key laboratory tests include:
- Creatine kinase (CK) levels, which are typically elevated at least 5 times above the upper limit of normal, though levels often reach 10,000-100,000 U/L or higher in severe cases
- Myoglobin levels, which can be elevated in blood and urine, causing tea or cola-colored urine
- Plasma potassium tests to assess for hyperkalemia
- Creatinine tests to evaluate kidney function Other laboratory findings may include elevated liver enzymes (AST, ALT), elevated LDH, hyperphosphatemia, and later, hypocalcemia. Urinalysis typically shows positive dipstick for blood without red blood cells under microscopy (due to myoglobinuria). According to the guidelines for the acute care of severe limb trauma patients, it is recommended to perform repeated bio-assessment combining plasma myoglobin, plasma creatine phosphokinase (CPK), and kalaemia measurements, as well as bladder catheterization to monitor hourly urine output and urine pH, which should be maintained at 6.5 1. Early diagnosis is crucial as prompt intervention with aggressive IV fluid therapy can prevent kidney damage and other serious complications. Additional tests, such as complete blood count, coagulation studies, and arterial blood gases, may be ordered to evaluate for complications, and tests to determine the underlying cause of rhabdomyolysis, such as toxicology screens, viral studies, or autoimmune markers, should also be considered depending on the clinical presentation.
From the Research
Rhabdomyolysis Diagnosis Lab
- Rhabdomyolysis is a serious syndrome that can lead to acute kidney injury (AKI) and is characterized by severe acute muscle injury resulting in muscle pain, weakness, and/or swelling with release of myofiber contents into the bloodstream 2.
- Laboratory tests used to diagnose rhabdomyolysis include serum creatine kinase (CK) and urine myoglobin levels, which are markedly elevated in patients with this condition 2.
- A study published in the European journal of emergency medicine found that myoglobin concentration was a better predictor of AKI than CK activity, and the myoglobin/CK ratio was a good predictor of AKI 3.
- Another study published in the European journal of anaesthesiology found that peak creatine kinase levels of at least 5000 Ul were 55% specific and 83% sensitive for the prediction of AKI requiring renal replacement therapy 4.
- The diagnosis of rhabdomyolysis can be supported by clinical examination, history, laboratory studies, muscle biopsy, and genetic testing, which can help differentiate acquired from inherited causes of rhabdomyolysis 2, 5.
Laboratory Markers
- Serum creatine kinase (CK) is a commonly used marker for the diagnosis of rhabdomyolysis, with levels more than five times the upper reference limit indicating the condition 3.
- Myoglobin levels are also elevated in rhabdomyolysis and can be used to predict the development of AKI 3, 2.
- The myoglobin/CK ratio has been proposed as a useful tool in the clinical evaluation of patients with rhabdomyolysis, with a ratio more than 0.2 associated with an increased likelihood of developing AKI 3.
Diagnostic Algorithm
- A practical diagnostic algorithm for rhabdomyolysis has been proposed, which includes clinical examination, history, laboratory studies, muscle biopsy, and genetic testing to differentiate acquired from inherited causes of the condition 2.
- The McMahon Score has been validated as a prognostic marker for AKI in patients with rhabdomyolysis, with a score of at least 6 calculated on admission allowing for a more sensitive, specific, and timely identification of patients who may benefit from high-volume fluid resuscitation 4.