Meta-analysis of randomised controlled trials for pre-bronchodilator (BD) outcomes stratified by age group

Outcome or subgroupStudies nParticipants nStatistical methodEffect estimatep-valueI2GRADE
ΔPre-BD FEV1 % pred88332MD (Random, 95% CI)2.22 (1.32–3.12)<0.000141%Moderate#
 Adults54181MD (Random, 95% CI)2.47 (1.64–3.29)<0.00010%High
 Children44151MD (Random, 95% CI)2.08 (0.71–3.44)0.00364%Moderate#
ΔPre-BD FEV1 mL43603MD (Random, 95% CI)74.14 (54.47–93.81)<0.000187%Moderate#
 Adults22634MD (Random, 95% CI)108.82 (84.40–133.23)<0.00010%High
 Children2969MD (Random, 95% CI)10.00 (−23.21–43.21)0.560%Moderate#
ΔPre-BD FEV1 SMD1011131SMD (Random, 95% CI)0.21 (0.12–0.30)<0.000168%Moderate#
 Adults66740SMD (Random, 95% CI)0.28 (0.15–0.41)<0.000163%Moderate#
 Children54391SMD (Random, 95% CI)0.16 (0.04–0.28)0.00860%Moderate#
ΔPre-BD FVC % pred2804MD (Fixed, 95% CI)0.10 (−1.23–1.43)0.880%Moderate#
 Adults175MD (Fixed, 95% CI)2.30 (−2.29–6.89)0.33Low#,
 Children1729MD (Fixed, 95% CI)−0.10 (−1.49–1.29)0.89Low#,
ΔPre-BD FVC mL2804MD (Random, 95% CI)−12.84 (−149.33–123.65)0.8553%Moderate#
 Adults175MD (Random, 95% CI)90.00 (−100.51–280.51)0.35Low#,
 Children1729MD (Random, 95% CI)−60.00 (−124.87–4.87)0.07Low,
ΔPre-BD FVC SMD2804SMD (Fixed, 95% CI)0.01 (−0.13–0.15)0.860%Moderate#
 Adults175SMD (Fixed, 95% CI)0.23 (−0.23–0.68)0.33Low#,
 Children1729SMD (Fixed, 95% CI)−0.01 (−0.16–0.14)0.89Low#,
ΔPre-BD FEV1/FVC % pred00MD (Fixed, 95% CI)
 Adults00MD (Fixed, 95% CI)
 Children00MD (Fixed, 95% CI)
ΔPre-BD FEV1/FVC ratio1729MD (Fixed, 95% CI)1.60 (0.64–2.56)0.001Moderate#
 Adults00MD (Fixed, 95% CI)
 Children1729MD (Fixed, 95% CI)1.60 (0.64–2.56)0.001Moderate#
ΔPre-BD FEV1/FVC SMD1729SMD (Fixed, 95% CI)0.25 (0.10–0.39)0.001Moderate#
 Adults00SMD (Fixed, 95% CI)
 Children1729SMD (Fixed, 95% CI)0.25 (0.10–0.39)0.001Moderate#

FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; MD: mean difference; SMD: standardised mean difference. #: GRADE score downgraded for heterogeneity or inconsistency of results between studies; : GRADE score downgraded for imprecision, 95% CI includes important benefit and potential harm.