| Methods |
Design: four group, four period cross‐over trial
Purpose: examine the effect of terbutaline, isotonic saline, ambient air and no‐treatment on chronic airway obstruction in asthmatics |
| Participants |
Patients: asthmatic out‐patients with reversible chronic airway obstruction
Baseline comparability: no carry‐over effect |
| Interventions |
Placebo:
‐inhalation of air from a noisy nebulizer
‐inhalation of isotonic saline from a noisy nebulizer
Untreated: inhalation of air through a mouthpiece disconnected from the nebulizer
Experimental: inhalation of terbutaline from a noisy nebulizer
(Co‐intervention: use of corticosteroids or bronchodilator drugs prohibited) |
| Outcomes |
Change in forced expiratory volume in 1 second (FEV1)
Change in forced vital capacity (FVC) |
| Notes |
The outcome data was not available from the first period only, and was calculated as deriving from a parallel group trial. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Adequate sequence generation? |
Unclear risk |
NS |
| Allocation concealment? |
Unclear risk |
NS |
| Blinding?
Treatment provider |
Low risk |
'The treatment was given double‐blind...' |
| Blinding?
Outcome assessor |
Low risk |
'... but the nurse in charge of spirometry did not know whether or not the patient was receiving treatment' |
| Incomplete outcome data addressed?
All outcomes |
High risk |
Drop‐out > 15% or NS |
| Free of selective reporting? |
Unclear risk |
No protocol available |
| Free of other bias? |
Unclear risk |
The outcome data from this cross‐over trial was not available from the first period only, and was calculated as deriving from a parallel group trial. |
| No signs of variance inequality or skewness? |
Unclear risk |
Not relevant (not naturally positive continuous outcomes e.g. change) |
| Trial size > 49? |
High risk |
N = 48 |
| Clearly concealed allocation + trial size > 49 + drop‐out max 15% |
High risk |
Trial size < 49 |
