Definitions of mild asthma: classification used in this review
| Main criteria for mild asthma | RCTs (n=54) | Observational/other studies (n=10) | ||
| All n (%) | Studies permitting past history of exacerbations n (%) | All n (%) | Studies permitting past history of exacerbations n (%) | |
| 1) Treatment level | 3 (5.6) | 0 (0) | 5 | 2 (20.0) |
| 2) Symptom frequency criteria | 3 (5.6) | 3 (5.6) | 0 | – |
| 3) FEV1 ≥80% pred and symptoms<daily | 19 (35.2) | 15 (27.8) | 2 | 1 (10.0) |
| 4) FEV1 >60–80% pred and symptoms<daily | 15 (27.8) | 13 (24.1) | 1 | 1 (10.0) |
| 5) Miscellaneous definitions# | 9 (16.7) | 8 (14.8) | 0 | – |
| 6) Included patients aged <5 years | 5 (9.3) | 4 (7.4) | 2 | 2 (20.0) |
RCT: randomised controlled trial; FEV1: forced expiratory volume in 1 s. # Miscellaneous definitions not captured by the other five categories (e.g. “doctor-diagnosed mild asthma”, or “mild asthma based on airway hyper-responsiveness” alone), or, studies that did not state that patients had “mild asthma” but included patients with disease characteristics similar to those in the other five categories.