CRP and interstitial lung disease: Of note, there were statistically negative correlations of serum Rcn3 level with TLC% pred, FVC% pred and DLCO% pred in CTD-ILD patients (r =  − 0.367, p = 0.039; r =  − 0.391, p = 0.027; r =  − 0.370, p = 0.037, respectively), whereases there were statistically positive correlations of serum Rcn3 level with CRP and ESR in patients with CTD-ILD (r = 0.355, p = 0.046; r = 0.392, p = 0.026, respectively).