TABLE 2

Summary of findings and subgroup analyses

Outcomes and subgroups	Participants (n)	Studies (n)	Mean difference (unsupervised− supervised)^#	LoA	95% CI	I² (%)	Anticipated impact (%)^¶
FEV₁ overall	4517	17	−106 mL	−509, 296	−129, −84	95.8	38.9
Low risk of bias	2679	4	−103 mL	−444, 238	−160, −46	96.2	38.6
At risk of bias	1178	14	−115 mL	−705, 475	−154, −75	95.9	39.9
Same day measurements	235	5	−65 mL	−421, 292	−129, −1	95.4	35
Non-same day measurements	3520	11	−144 mL	−561, 272	−184, −105	95.3	43.8
Adults	3627	14	−103 mL	−517, 311	−134, −73	93.6	38.6
Children	230	4	−132 mL	−410, 146	−222, −42	98.2	42.1
FVC overall	1307	17	−184 mL	−1028, 660	−253, −114	96	66.9
Low risk of bias	238	4	−118 mL	−886, 650	−201, −35	88.5	65.2
At risk of bias	1069	13	−207 mL	−1098, 684	−300, −114	96.6	67.7
Same day measurements	106	2	−14 mL	−287, 260	−42, 15	0	63.9
Non-same day measurements	1099	13	−228 mL	−1239, 783	−285, −171	85.3	68.4
Adults	1215	16	−198 mL	−1162, 766	−262, −134	92.5	67.7
FEF_25–75%	146/899	3	−19 mL·s⁻¹	−497, 458	−329, 291	99.7	41.3
PEF	124/400	2	−92 mL·s⁻¹	−498, 314	−110, −74	0	38.1

The standard deviation was imputed for five studies so mean differences could be calculated after efforts were made to obtain data from authors [30, 37, 38, 40, 49]. LoA: limits of agreement; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; FEF_25–75%: forced expiratory flow at 25–75% of the FVC; PEF: peak expiratory flow. ^#: a negative mean difference indicates unsupervised spirometry is lower. ^¶: percentage of results that would probably have a difference >200 mL.