Specialized Tests of Muscle Damage

Muscle biopsy, detection of antibodies to various muscle components and neuromuscular antigens, electromyography, and molecular genetic studies are necessary to diagnose many muscle disorders, particularly species and breed-associated myopathies. Other disorders will require complete clinical, histologic, pathophysiologic, and genetic description in order to develop reliable diagnostic tests.

Newer serum tests being evaluated in veterinary medicine are myosin light-chain assays for the diagnosis of inflammatory muscle disease and myocardial infarction, and cardiac troponin I assays, also with potential application for the diagnosis of acute myocardial diseases. In cats, tests measuring B-type natriuretic peptide concentrations in pleural fluid have emerged to help distinguish cardiac and non-cardiac causes of respiratory distress.

Clinical evaluation for mitochondrial or lipid-storage myopathies is difficult even with the help of muscle biopsies. These cases may require specialized tests such as organic acid analysis, plasma amino analysis, and carnitine analysis for diagnosis.

Although not currently offered by diagnostic laboratories, serum aldolase may be measured more routinely in the future as elevated aldolase activities can help confirm suspected myopathy in cases where CK activity is low to normal.