RCN3 and idiopathic pulmonary fibrosis: In addition, the levels of CRP (P = 0.044), ESR (P = 0.026) and serum Rcn3 (p = 0.006) in CTD-ILD group were significantly higher than those in IPF group, Cohen’s d = 0.631 for the difference of serum Rcn3 between IPF and CTD-ILD patients.