| Total | 342 |
| Mean age in years (SD) | 54 (14) |
| Female gender | 222 (65%) |
| Pre-test working diagnosis |
| Suspected IIM | 92 (26.9%) |
| CTDs without IIM | 137 (40.1%) |
| Myopathic syndromes with low likelihood of IIM | 113 (33.0%) |
| Final diagnosis and subtype |
| IIM | 67 (19.6%) |
| Overlap myositis | 21 |
| Dermatomyositis | 12 |
| Polymyositis | 11 |
| Antisynthetase syndrome | 7 |
| Amyopathic dermatomyositis | 7 |
| Inclusion body myositis | 5 |
| Immune mediated necrotizing myopathy | 4 |
| CTD without IIM | 120 (35.1%) |
| Systemic sclerosis | 91 |
| Undifferentiated CTD | 10 |
| Systemic lupus erythematosus | 7 |
| Inflammatory arthritis | 6 |
| Overlap CTD | 4 |
| Sjogrens syndrome | 2 |
| Non-IIM/CTD | 155 (45.3%) |
| Other rheumatologic diagnoses | 45 |
| Other neurologic diagnoses | 12 |
| Genetic myopathy | 11 |
| Endocrinologic myopathy | 5 |
| Idiopathic pulmonary fibrosis | 3 |
| Post-viral myopathy | 3 |
| Traumatic myopathy | 3 |
| Familial amyloidosis | 1 |
| Orbital myositis | 1 |
| Malignancy | 1 |
| Unclear | 70 |
