Table S3.

Corrected difference of THBG levels between groups by multivariate models

Variables	Covariance analysis	Multivariate linear regression
COPD vs control
Group (COPD vs control)	P=0.000	P=0.000
Age, years	P=0.969	P=0.969
Smoking history, pack-years	P=0.264	P=0.264
Hypertension	P=0.957	P=0.957
GOLD I–IV vs control
Group (GOLD I–IV vs control)	P=0.000	P=0.000
Age, years	P=0.536	P=0.621
Smoking history, pack-years	P=0.211	P=0.227
Smoking cessation duration, years	P=0.620	P=0.402

Notes: Covariance analysis and multivariate linear regression model, which were corrected for age, smoking history, and hypertension between COPD and controls, indicated that the group (COPD vs control) is the unique variable influencing THBG levels. Similarly, multivariate models, which were corrected for age, smoking history, and smoking cessation duration among controls, GOLD I–IV, implied that the group (GOLD I–IV vs control) is the independent factor against THBG levels.

Abbreviations: COPD, chronic obstructive pulmonary disease; GOLD, Global Initiative for Obstructive Lung Disease; THBG, thyroxine-binding globulin.