Table 2.

Correlations between spirometry, histogram characteristics and CT-density scores

	FEV1		FVC
	R	P value	R	P value
Histogram characteristics
- MLD	−0.22	0.084	− 0.31	0.012
- Mode	0.14	0.285	0.11	0.397
- SD	−0.63	< 0.001	− 0.67	< 0.001
- Kurtosis	0.56	< 0.001	0.65	< 0.001
- Skewness	0.60	< 0.001	0.67	< 0.001
CT-density score with fixed thresholds
- (−) 400 HU	−0.51	< 0.001	−0.59	< 0.001
- (−) 500 HU	−0.53	< 0.001	− 0.61	< 0.001
- (−) 600 HU	− 0.54	< 0.001	−0.61	< 0.001
CT-density score with adapted thresholds
- MLD + 2 SD	−0.62	< 0.001	−0.67	< 0.001
- MLD + 1 SD	−0.68	< 0.001	− 0.71	< 0.001
- Mode + 500 HU	− 0.57	< 0.001	−0.64	< 0.001
- Mode + 400 HU	−0.60	< 0.001	− 0.65	< 0.001
- Mode + 300 HU	− 0.64	< 0.001	−0.70	< 0.001
- Mode + 3 SD	−0.54	< 0.001	− 0.62	< 0.001
- Mode + 2 SD	− 0.65	< 0.001	−0.70	< 0.001
- Mode + 1SD	−0.66	< 0.001	− 0.68	< 0.001

Definition of abbreviations: CT computed tomography, FEV₁ forced expiratory volume in 1 s, FVC forced vital capacity, HU Hounsfield unit, MLD Mean Lung Density, SD Standard Deviation