Diagnostic and prognostic value of anti-CarP antibodies in a sample of Egyptian rheumatoid arthritis patients

Detection of autoantibodies in sera of rheumatoid arthritis (RA) patients has an important role in diagnosis and management strategies. Recently, another type of autoantibodies has been detected with activity against carbamylated proteins (anti-CarP) which may play an important role in the diagnosis of RA. The aim of this study was to raise knowledge about the diagnostic and prognostic value of anti-CarP antibodies in RA.

Seventy RA patients and thirty-four controls were included in this study. DAS28 was used to evaluate disease activity. Joint erosions were assessed by Larsen score using plain X-ray of involved joints of hands and feet. Serum samples were analyzed for anti-CarP antibody titer using the ELISA technique.

Out of 70 patients, 35.7% were positive for anti-CarP and only 5.88% of controls had high titer above the cut-off value. A total of 24.29% of the patients were RF-negative and 30% were ACPA-negative. Five patients (29.41%) of the negative RF group were positive for anti-CarP. Four patients (19%) of the ACPA-negative group were positive for anti-CarP, and three patients (4.28%) of the total number of patients were triple negative and seventeen (24.28%) were triple positive. There was a significant correlation between anti-CarP titer and both DAS28 and Larsen scores only in the positive anti-CarP group. In addition, there was a strong association between anti-CarP antibody titer and joint erosions at both baseline and after 1-year follow-up.

Presence of the anti-CarP antibodies in sera of RA patients may have a prognostic value as it correlates with the disease activity and joint erosions; moreover, it may have a diagnostic value in rheumatoid arthritis especially in RF- and ACPA-negative patients.