Table 5.

Correlation analysis between serum levels of PICP, clinical variables, and inflammatory biomarkers

Variables	Serum levels of PICP
	r	P-value
Smoking (pack-year)	0.134	0.411
FEV1 %pred (%)	−0.250	0.119
FEV1/FVC% (%)	−0.251	0.118
CRP (mg/L)	0.077	0.646
IL-6 (pg/mL)	0.483	<0.001
IL-8 (pg/mL)	0.472	0.001
TNF-α (pg/mL)	0.220	0.147

Abbreviations: PICP, procollagen type I C-terminal peptide; %pred, percentage of predicted; CRP, C-reactive protein; TNF, tumor necrosis factor.