Analysis of possible relationships between serum CHIT1 activity and YKL-40 concentration and clinical measures in patients with IPF revealed a positive correlation between serum YKL-40 and age of IPF subjects at baseline (r=0.56, p<0.01, Table S1), 6 months (r=0.48, p<0.05, Table S2), 12 months (r=0.45, p<0.05, Table S3), and 18 months of antifibrotic treatment (r=0.41, p<0.05, Table S4). This evidence concerns the gene CHIT1 and idiopathic pulmonary fibrosis.