Abstract:

Objective To analyze the level of anti-carbamylated protein （Carp） antibody in patients with rheumatoid arthritis （RA）,and to investigate the role of anti-Carp antibody in the diagnosis and evaluation of RA. Methods The levels of serum anti-Carp IgG and anti-Carp IgA antibodies in RA group （102 cases）,non-RA group （55 cases） and healthy control group （83 cases） were determined by enzyme-linked immunosorbent assay（ELISA）. The difference of the 2 indices among the 3 groups and the relationship between anti-Carp antibody and RA were evaluated. Results The level of anti-Carp IgG antibody in serum of RA group was （8.60±2.64）U/L,and the positive rate was 42.16%. The level of anti-Carp IgA antibody in serum of RA group was （6.65±3.09）U/L,and the positive rate was 46.08%,which were higher than those in non-RA group and healthy control group （P<0.05）. The positive rate of anti-Carp IgG antibody was 46.67%,and the positive rate of anti-Carp IgA antibody was 33.33% in anti-cyclic citrullinated peptide （CCP） antibody negative RA patients. The levels of IgG,IgA and IgM in anti-Carp IgG antibody positive group had statistical significance compared with those in anti-Carp IgG antibody negative group （P<0.05）,and the levels of IgG,IgA,IgM and complement （C）4 in anti-Carp IgA antibody positive group were higher than those in anti-Carp IgA antibody negative group （P<0.05）. There was no correlation of anti-Carp IgG antibody with anti-CCP antibody and rheumatoid factor（RF） （P>0.05）,and there was no correlation of anti-Carp IgA antibody with anti-CCP antibody and RF （P>0.05）.Conclusions Anti-Carp antibody is a new serological marker for the diagnosis of RA,and it may be associated with the severity of the disease,which may contribute to the diagnosis of anti-CCP antibody negative RA.

Key words: Anti-carbamylated protein antibody, Rheumatoid arthritis, Autoantibody