Comparison 1. Alpha‐1 antitrypsin versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Forced expiratory volume in 1 second (FEV1), change (mL or %)	3	283	Std. Mean Difference (IV, Fixed, 95% CI)	‐0.19 [‐0.42, 0.05]
2 Carbon monoxide diffusion, change (mmol/minute/kPa or %)	3	283	Std. Mean Difference (IV, Fixed, 95% CI)	‐0.11 [‐0.35, 0.12]
3 Computer tomography (CT) lung density, change (g/L)	3	273	Mean Difference (IV, Fixed, 95% CI)	0.86 [0.31, 1.42]