| Study characteristics |
| Methods |
Double‐blind, randomised, parallel group controlled trial |
| Participants |
Adults and children 12 years and over with at least six month history of asthma, needing GINA step 1 or 2. Mean age was 41 years and 2.5% were current smokers. 62% were female. Mean pre bronchodilator FEV1 was 84% predicted. 78% had had no severe asthma exacerbations in the prior 12 months. |
| Interventions |
Budesonide/formoterol 200 μg / 6 μg turbohaler as required (with twice daily placebo) versus budesonide 200 μg twice per day plus terbutaline 500 μg as required. |
| Outcomes |
Annual severe asthma exacerbation rate, time to first severe exacerbation, asthma related discontinuation, change from baseline FEV1, as needed drug use, ACQ‐5, AQLQ(S), percentage of controller use days. |
| Notes |
Funded by AstraZeneca |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Low risk |
Computer‐generated randomisation codes |
| Allocation concealment (selection bias) |
Low risk |
Multiple allocation concealment measures |
| Blinding (performance bias and detection bias)
All outcomes |
Low risk |
Multiple measures to preserve blinding |
| Blinding of participants and personnel (performance bias)
All outcomes |
Low risk |
Multiple measures to preserve blinding |
| Blinding of outcome assessment (detection bias)
All outcomes |
Low risk |
Multiple measures to preserve blinding |
| Incomplete outcome data (attrition bias)
All outcomes |
Low risk |
9% loss to follow up, appears balanced across groups |
| Selective reporting (reporting bias) |
Low risk |
Final report matches published protocol |
