Table 3– Correlation between disease duration, high-resolution computed tomography (HRCT) airway wall thickening and HRCT air trapping

HRCT variables	Disease duration
	Spearman rank	p-value
Visual score air trapping	-0.061	0.676
Visual score airway wall thickening	0.089	0.536
Wall area percentage	-0.061	0.671
WA_BSA	-0.038	0.797
WA_%age	-0.274	0.052
AT_HU-850	0.417	0.004
AT₁₅	-0.382	0.008

WA_BSA: wall area normalised to body size; WA_%age: wall area percentage corrected for age; HU: Hounsfield units; AT_HU-850: number of voxels < -850 HU as percentage of total number of voxels; AT₁₅: HU at 15th percentile.