Spirometry parameters used to define small airways obstruction in population-based studies: systematic review

Respiratory Research

Table 2 Meta-regression of covariates on prevalence of SAO

	Coefficient (% change in prevalence)	95% CI	p value
Spirometry parameter
FEF_25–75	(Ref)	–	–
FEF_25–75/VC	− 14.3	− 38.6, 10.0	0.250
FEF₅₀/FEF₂₅	9.7	5.9, 13.4	< 0.001
FEV₃/FVC	− 5.7	− 9.3, − 2.1	0.002
FEF₅₀	− 19.3	− 23.1, − 15.6	< 0.001
WHO region
Americas	(ref)	–	–
European	24.3	3.0, 45.6	0.025
Western Pacific	5.3	3.0, 7.5	< 0.001
South East Asia	4.1	− 18.7, 26.9	0.726

p < 0.05 = significant. FEF_25–75: Mean expiratory flow rate between 25 and 75% of the FVC, FEF_25–75/VC: Mean expiratory flow rate between 25 and 75% of the FVC as a ratio of the vital capacity. FEF₅₀: Forced expiratory flow rate at 50% of the FVC. FEF₅₀/FEF₂₅: Forced expiratory flow at 50% of the FVC as a ratio or the forced expiratory flow with 25% of the FVC remaining, FEV₃/FVC: forced expiratory volume in 3 s as a ratio of the FVC

ISSN: 1465-993X