Table 4. Multiple Linear Regression Analysis for CT-Quantitative EAtC Mapping and Clinical Variables (Age, Pack-Years) for PFTs and BODE Index.

Variables		Coefficients	P	R2
FEV1				0.352
	fAT	−0.409	< 0.001
	Emph	−0.188	< 0.001
FEV1/FVC				0.488
	fAT	−0.277	< 0.001
	Emph	−0.224	< 0.001
FEF25–75%				0.264
	fAT	−0.281	< 0.001
RV/TLC				0.233
	fAT	0.344	< 0.001
DLCO				0.303
	Emph	−0.891	< 0.001
	Age	−0.153	0.038
BODE index				0.397
	fAT	0.425	< 0.001
	Emph	0.253	< 0.001
	Age	0.087	0.022

The following independent variables were used for the multivariable model: EAtC classes (fAT and Emph), age, and smoking history (pack-years). Normal from the EAtC classes was not considered as an independent variable because considerable multicollinearity (variance inflation factor > 10) between fAT and Normal were found. BODE = Body mass index, airflow Obstruction, Dyspnea and Exercise capacity, DL_CO = carbon monoxide diffusing capacity corrected for hemoglobin concentration, EAtC = emphysema air-trapping composite, Emph = emphysema by EAtC, fAT = functional air trapping by EAtC, FEF_25–75% = mean forced expiratory flow between 25% and 75% of FVC, FEV₁ = forced expiratory volume in 1 second, FVC = forced vital capacity, Normal = normal lung parenchyma by EAtC, PFT = pulmonary function test, RV = residual volume, TLC = total lung capacity