ALTHOUGH the diagnosis of polymyositis depends on a combination of clinical, pathologic, and laboratory findings, the significance and importance of abnormal results to various laboratory tests in cases of polymyositis is controversial. To determine which tests are helpful in diagnosing, evaluating the activity, and determining the clinical course and prognosis of the disease, data on 102 patients with polymyositis who had not received steroid therapy before their examination at the Mayo Clinic were analyzed. Two of the important laboratory procedures, electromyography and muscle biopsy, require special analysis and will be considered in a subsequent publication.
An analysis of the effects of steroid therapy on the same group of 102 patients was reported previously.1
Materials and Methods
All of the patients were thought to present a characteristic picture of the syndrome of active polymyositis. In 80 of the cases, the disease was chronic; in 11 cases, it was acute and