Paired inspiratory-expiratory chest CT scans to assess for small airways disease in COPD

Respiratory Research

Table 6 Regression models for lung function, exercise capacity and symptoms in subjects with severe emphysema

A. Linear regression for FEV₁ (L)
	Exp₋₈₅₆		E/I MLA		RVC_856-950
Independent variables	β*	p-value	β*	p-value	β*	p-value
% emphysema (Insp₋₉₅₀)	0.01	0.5	−0.08	< 0.0001	−0.01	0.3
Gas Trapping variable†	−0.46	< 0.0001	−0.43	< 0.0001	−0.46	< 0.0001
Model fit statistics
R²	0.63		0.68		0.67
B. Linear regression for FEV₁/FVC
	Exp₋₈₅₆		E/I MLA		RVC_856-950
Independent variables	β*	p-value	β*	p-value	β*	p-value
% emphysema (Insp₋₉₅₀)	−0.01	0.004	−0.03	< 0.0001	−0.02	< 0.0001
Gas Trapping variable†	−0.08	< 0.0001	−0.07	< 0.0001	−0.07	< 0.0001
Model fit statistics
R²	0.52		0.52		0.49
C. Linear regression for FEF_25-75
	Exp₋₈₅₆		E/I MLA		RVC_856-950
Independent variables	β*	p-value	β*	p-value	β*	p-value
% emphysema (Insp₋₉₅₀)	0.01	0.3	−0.04	0.0001	−0.004	0.7
Gas Trapping variable†	−0.24	< 0.0001	−0.23	< 0.0001	−0.24	< 0.0001
Model fit statistics
R²	0.46		0.50		0.49
D. Linear regression for 6-minute walk distance (ft).
	Exp₋₈₅₆		E/I MLA		RVC_856-950
Independent variables	β*	p-value	β*	p-value	β*	p-value
% emphysema (Insp₋₉₅₀)	−66.6	< 0.0001	−51.7	< 0.0001	−46.6	0.0002
Gas Trapping variable†	41.4	0.01	−3.4	0.8	−22.4	0.2
Model fit statistics
R²	0.41		0.41		0.41
E. Linear regression for SGRQ Total score.
	Exp₋₈₅₆		E/I MLA		RVC_856-950
Independent variables	β*	p-value	β*	p-value	β*	p-value
% emphysema (Insp₋₉₅₀)	0.9	0.2	0.9	0.1	0.1	0.8
Gas Trapping variable†	1.1	0.2	3.0	0.0001	4.4	< 0.0001
Model fit statistics
R²	0.34		0.35		0.36

All models are adjusted for age, sex, race, clinical center, current smoking status, pack-years of smoking, height, weight, Siemens 64 scanner. Models for 6-minute walk distance (D) and SGRQ score (E) were additionally adjusted for FEV1% predicted.
*Independent variables standardized to mean = 0 and SD = 1. β = change in dependent variable, e.g. FEV₁ (L), for each SD change in independent variable.
†Either Exp₋₈₅₆, E/I mean lung attenuation ratio, or RVC_856-950.

ISSN: 1465-993X