| Study | O'Byrneet al. 5 | Sontet al. 3 | Greenet al. 4 |
| Participants | Moderate persistent asthma | Mild (? persistent) asthma | Severe asthma |
| Sample size n | 2760 | 75 | 74 |
| Treatment adjustment | SMART | Airway hyperresponsiveness | Sputum eosinophils |
| Outcome | Severe exacerbation | Mild exacerbation | Severe exacerbation |
| Number needed to treat | 11 | 5 | 5 |
SMART: Symbicort® (budesonide/formoterol) as Maintenance And Reliever Therapy.