Univariate logistic regression analysis indicated that age >65 years, male sex, LDH >245 U/L, CRP >10 mg/L, CEA >5 μg/L, CA-199 > 35 U/mL, CA-125 > 35 U/mL, CA-153 > 35 U/mL, FVC <60% predicted, DLCO <50% predicted and UIP-like pattern on chest HRCT were all potential factors associated with the progression of f-ILD to PPF. Here, CRP is linked to interstitial lung disease.