CHI3L1 and rheumatoid arthritis: In both IPF and RA-ILD patients, MMP-7 and ACPA levels were significantly higher compared to RA patients, and serum CHI3L1 levels could differentiate IPF from RA-ILD (245.8 ± 180.2 ng/mL vs. 116.0 ± 58.3 ng/mL, p<0.001) and predict survival, offering potential value in identifying highly specific biomarkers.