Summary of eligible studies
| Characteristics | Included studies (n=42) |
| Region | |
| America | 8 (19.0) |
| Asia | 8 (19.0) |
| Europe | 17 (40.5) |
| Others | 9 (21.4) |
| Study design | |
| Retrospective | 38 (90.5) |
| Prospective | 4 (9.5) |
| Case-control | 4 (9.5) |
| Cohort | 38 (90.5) |
| Sample size | 112.5 (18–656) |
| Definition of acute severe ulcerative colitis | |
| Truelove and Witts criteria | 30 (71.4) |
| Other criteria | 12 (28.6) |
| Follow-up period | |
| ≤12 months | 14 (33.3) |
| >12 months | 28 (66.7) |
| Concomitant medications | |
| Corticosteroids | 38 (90.5) |
| Infliximab | 26 (61.9) |
| Ciclosporin | 23 (54.8) |
| Others | 15 (35.7) |
Data were presented as counts N (percentage) or median (range).