Baseline* characteristics of the whole population
| (n=number of treatment episodes) | Control group (n=1260) | Prophylaxis group (n=262) | P value |
| Male gender, n (%) | 374 (29.7) | 89 (34.0) | 0.170 |
| Age, year, mean (SD) | 41.2 (15.2) | 46.2 (16.0) | <0.001 |
| Disease duration, year, mean (SD) | 3.0 (3.8) | 2.5 (4.0) | 0.053 |
| Underlying disease | |||
| Systemic lupus erythematosus, n (%) | 636 (50.5) | 122 (46.8) | 0.249 |
| Systemic sclerosis, n (%)† | 30 (2.4) | 5 (1.9) | 0.642 |
| Dermatomyositis, n (%) | 100 (7.9) | 38 (14.5) | 0.001 |
| Polymyositis, n (%) | 54 (4.3) | 12 (4.6) | 0.831 |
| GPA, n (%) | 38 (3.0) | 18 (6.9) | 0.003 |
| MPA, n (%) | 9 (0.7) | 11 (4.2) | <0.001 |
| EGPA, n (%) | 43 (3.4) | 7 (2.7) | 0.541 |
| Polyarteritis nodosa, n (%) | 17 (1.3) | 7 (2.7) | 0.118 |
| Rheumatoid arthritis, n (%)† | 58 (4.6) | 10 (3.8) | 0.575 |
| Adult-onset Still’s disease, n (%) | 31 (2.5) | 9 (3.4) | 0.369 |
| Behcet’s disease, n (%) | 182 (14.4) | 12 (4.6) | <0.001 |
| Cryoglobulinaemic vasculitis, n (%) | 1 (0.1) | 2 (0.8) | 0.023 |
| Ankylosing spondylitis, n (%) | 12 (1.0) | 0 (0.0) | 0.113 |
| Primary Sjogren’s syndrome, n (%) | 3 (0.2) | 0 (0.0) | 0.429 |
| Others, n (%)‡ | 47 (3.7) | 9 (3.4) | 0.817 |
| Initial steroid dose of 30–45 mg PD, n (%) | 426 (33.8) | 88 (33.6) | 0.945 |
| Initial steroid dose of 45–60 mg PD, n (%) | 141 (11.2) | 42 (16.0) | 0.028 |
| Initial steroid dose of ≥60 mg PD, n (%) | 696 (55.0) | 132 (50.4) | 0.172 |
| Concomitant immunosuppressive treatment | |||
| Steroid pulse treatment, n (%) | 164 (13.0) | 99 (37.8) | <0.001 |
| Oral cyclophosphamide, n (%) | 49 (3.9) | 34 (13.0) | <0.001 |
| Cyclophosphamide pulse treatment, n (%) | 99 (7.9) | 67 (25.6) | <0.001 |
| Cumulative steroid dose, mean (SD)§ | 1597.1 (1568.7) | 3119.7 (1821.5) | <0.001 |
| Lymphopenia, n (%)¶ | 283 (22.5) | 87 (33.2) | <0.001 |
*The baseline date was defined as the day on which PCP prophylaxis (prophylaxis group) or high-dose steroid (control group) was started.
†The main reason for the use of high-dose steroids in these diseases was associated interstitial lung disease.
‡Including Takayasu’s arteritis, temporal arteritis and relapsing polychondritis.
§Cumulative steroid (prednisone) dose during the previous 6 months.
¶Defined as <800 lymphocytes/mL.
EGPA, eosinophilic granulomatosis with polyangiitis; GPA, granulomatosis with polyangiitis; MPA, microscopic polyangiitis; PCP, pneumocystis pneumonia; PD, prednisone.