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

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

A. Linear regression for FEV1 (L)
  Exp−856 E/I MLA RVC856-950
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 RVC856-950
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 FEF25-75
  Exp−856 E/I MLA RVC856-950
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 RVC856-950
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 RVC856-950
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
  1. 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.
  2. *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.
  3. †Either Exp−856, E/I mean lung attenuation ratio, or RVC856-950.