Compared with RA-N-DM group, the levels of IgG (Z=−2.826, p<0.05), IgM (Z=−2.827, p<0.01), ALB (Z=−4.957, p<0.001) and A/G (Z=−3.095, p<0.05) in RA-DM group were significantly reduced, CRP (Z=−2.078, p<0.05), FBG (Z=−10.85, p<0.001) and GLB (Z=−2.349, p<0.05) were increased. Here, CRP is linked to rheumatoid arthritis.