Investigative strategies for muscle pain.

Muscle pain is the presenting symptom in patients with a wide variety of conditions. Such patients often pose problems in diagnosis and management and a rational scheme for their investigation is needed. The results of muscle biopsy, electromyography, exercise and strength testing and blood measurements in 109 consecutive patients presenting with myalgia are reported. By determining the sensitivity and specificity of the tests in identifying patients with specific muscle abnormalities, a rational investigative protocol has been constructed. Creatine kinase and erythrocyte sedimentation rate are the most useful screening tests and if either is abnormal, muscle biopsy, electromyography, muscle strength and exercise testing are then performed. Despite exhaustive investigation, specific muscle abnormalities were found in only one-third of the patients; whilst many of the remaining patients undoubtedly had a psychogenic component to their pain, it is likely that a number of unidentified specific metabolic defects remain as causes of myalgia.