CRP and rheumatoid arthritis: Our meta-analysis results show that in RA-ILD patients, CRP, ESR, anti-CCP antibodies, RF, KL-6, SP-D, CEA, CA19-9, MMP-7, CXCL-10, and NLR are all significantly higher than in RA patients, which indicates promising prospects for distinguishing between RA and RA-ILD patients.