Demographic data and clinical characteristics of cases and controls
| Cases | Controls | ||
|---|---|---|---|
| Gender, n (%) | 149 | 290 | |
| Male | 52 (35) | 98 (34) | |
| Female | 97 (65) | 192 (66) | |
| Age, year (at blood sampling) | |||
| Median (range) | 56 (18–72) | 41 (18–70) | |
| Disease duration,* (months) | – | ||
| Median (range) | 6.5 (0–368) | ||
| Disease duration,* n (%) | – | ||
| ≤3 m | 66 (44) | ||
| >3 m | 83 (56) | ||
| Subdiagnosis, n (%) | – | ||
| PM | 76 (51) | ||
| DM | 52 (35) | ||
| IBM | 15 (10) | ||
| JDM | 6 (4) | ||
| Autoantibodies | |||
| Anti-Jo-1, n (%) | 23 (16) | 145† | – |
| Other AsAb‡, n (%) | 3 (2) | 130† | – |
| Anti-SSA§, n (%) | 44 (34) | 130† | – |
| Anti-SSB, n (%) | 7 (6) | 128† | – |
| Anti-Mi-2, n (%) | 3 (7) | 43† | – |
| Anti-SRP, n (%) | 5 (6) | 84† | – |
*Disease duration calculated from diagnosis to date of blood sampling.
†Total number of cases with available results from antibody analysis.
‡anti-PL-7, anti-PL-12, anti-EJ, anti-OJ, anti-KS, anti-ZO.
§SSA/Ro52 and/or SSA/Ro60: six patients had an overlap syndrome (rheumatoid arthritis in 1, systemic sclerosis in 2, Sjögren's syndrome in 2, mixed connective tissue disease in 1).
AsAb, anti-synthetase antibody; DM, dermatomyositis; IBM, inclusion body myositis; JDM, juvenile dermatomyositis; PM, polymyositis; SSA, Sjögren's syndrome antigen A, SSB, Sjögren's syndrome antigen B; SRP, signal recognition particle.