Table 2

Unadjusted correlation of baseline characteristics and disease severity with calprotectin serum levels in the three study groups

Calprotectin levels	Healthy controls		Derivation IPF cohort		Validation IPF cohort
Variables	r	P value	r	P value	r	P value
Sex, men		0.03		0.81		0.15
Age, years	0.17	0.39	−0.02	0.91	−0.16	0.20
BMI, kg/m²	0.50	0.009	0.12	0.63	0.01	0.94
Ever-smokers		0.60		0.35		0.08
Pack-years	0.03	0.88	0.62	0.07	0.14	0.28
DLCO, % predicted	0.31	0.12	−0.53	0.007	−0.23	0.06
FVC, % predicted	0.12	0.56	0.02	0.90	−0.13	0.29
FEV₁, % predicted	0.13	0.54	0.33	0.20	−0.03	0.78
CPI	−0.31	0.13	0.66	0.007	0.22	0.08

BMI, body mass index; CPI, Composite Physiological Index; DLCO, diffusing capacity for carbon monoxide; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; IPF, idiopathic pulmonary fibrosis; r, correlation coefficient.