Summary of findings for the main comparison. Beta2‐agonists compared with placebo (single administration) for exercise‐induced asthma.
| Beta2‐agonists compared with placebo (single administration) for exercise‐induced asthma | ||||||
| Patient or population: exercise‐induced asthma Intervention: beta2‐agonists Comparison: placebo (single administration) | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No. of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| Placebo (single administration) | Beta2‐agonists | |||||
| Maximal percentage fall in FEV1 | The mean fall in FEV1 in the intervention group was MD 17.67 lower (19.51 lower to 15.84 lower)a | － | 799 (72 studies)a,b,c | ⊕⊕⊕⊝ moderated,e,f | The results in the subgroup of LABA and SABA were similar: MD 15.6 lower (18.29 lower to 12.92 lower) and MD 18.99 lower (21.38 lower to 16.6 lower) in 44 and 28 studies, respectively | |
| Number of participants with an FEV1 fall > 10% | 843 per 1000 (84.3)% | 300 per 1000 (243 to 410) | OR 0.08 (0.06 to 0.13) | 773 (19 studies) | ⊕⊕⊕⊝ moderated,e | |
| Maximal percentage fall in PEF | The mean maximal percentage fall in PEF in the intervention group was MD 24.61 lower (37.57 lower to 11.65 lower)1 | － | 92 (14 studies)b | ⊕⊕⊝⊝ lowd,e,g | ||
| Maximal percentage fall in FEF25‐75% | The mean maximal percentage fall in FEF25‐75% in the intervention group was MD 20.75 lower (27.17 lower to 14.32 lower)1 | － | 106 (8 studies)b | ⊕⊕⊝⊝ lowd,e,g | ||
| Side effects | 50 per 1000 (5.0)% | 42 per 1000 (22 to 77) | OR 0.83 (0.43 to 1.59) | 2165 (55 studies)h | ⊕⊕⊝⊝ lowe,g,I | |
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; FEF25‐75%: forced expiratory flow 25–75%; FEV1: forced expiratory volume in 1 minute; LABA: long‐acting beta2‐agonist; MD: mean difference; OR: odds ratio; peak expiratory flow (PEF); SABA: short‐acting beta2‐agonist. | ||||||
| GRADE Working Group grades of evidence. High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
aLower indicates that beta2‐agonists are better than placebo.
bIn 51 studies that provided data for subgroup analysis, no difference was observed in the maximal percentage fall in FEV1, but the heterogeneity of the effect was seen primarily in the paediatric population.
cThese represent 72 study arms from 53 studies.
dIt is unclear how directly pulmonary function measures relate to what participants feel.
eThere was concern about lack of concealment, loss to follow‐up and reporting bias.
fInconsistency was moderate to high and was explained in part by subgroup analyses of adults and children.
gSmall numbers of participants were included with resulting wide confidence intervals.
hThese represent 55 study arms rather than studies.
iThis represents a mix of outcomes, and not all of them are of equal importance to patients.