Workup
Laboratory Studies
The following laboratory tests may be used to evaluate patients with myopathies:
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Creatine kinase (CK) with isoenzymes
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Electrolytes (calcium, magnesium)
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Serum myoglobin
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Serum creatinine and blood urea nitrogen (BUN)
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Urinalysis - Myoglobinuria is indicated by positive urinalysis with few red blood cells (RBCs) on microscopic evaluation.
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Complete blood count (CBC)
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Erythrocyte sedimentation rate (ESR)
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Thyroid function tests
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Aspartate aminotransferase (AST)
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Other Tests
Electrocardiography
Electrocardiographic (ECG) findings suggestive of hypokalemia include the following:
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Diffuse nonspecific ST-T wave changes
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Increased PR interval
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U waves
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Wide QRS
Other studies
Steroid therapy should be withheld until a definitive diagnosis is made, but many tests that are essential for distinguishing among the varied causes of myopathy are out of the scope of the emergency physician. These tests include the following:
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Genetic testing
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Magnetic resonance imaging (MRI) [10]
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Electromyography (EMG)
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