Diagnostic value of rheumatoid factor, antikeratin antibodies and anticyclic citrullinated peptide antibodies in rheumatoid arthritis: association with erosive articular damage

ABSTRACT

Various autoantibodies have been described in the serum of rheumatoid arthritis [RA] patients such as rheumatoid factor [RF], antikeratin antibodies [AKA] and anti-cyclic citrullinated peptide antibodies [anti-CCP]. This work was preformed to assess and compare the diagnostic value of RF, AKA and anti-CCP in RA, and to identify their predictive value for erosive articular damage in patients with RA. The study was carried out on 50 patients, 30 RA patients and 20 patients with other different rheumatic disorders who served as a control group. RA patients were 15 with early RA [<2 years disease duration] and 15 with late RA [>2 years]. Serum samples from all 50 patients were subjected to detection of IgM RF and anti-CCP by enzyme linked immunosorbent assay [ELISA] and AKA by indirect immunofluorescence. Erosive articular damage was quantified using the Larsen score. Positive anti-CCP was found in 23 out of 30 RA patients and in 2 out of 20 controls with the highest sensitivity and specificity for RA 76.7% and 90%, respectively. IgM RF was positive in 21 out of 30 RA patients and in 3 out of 20 controls with sensitivity and specificity of 70% and 85%, respectively. Lastly AKA was positive in 16 out of 30 RA patients and 4 out of 20 controls with the lowest sensitivity and specificity for diagnosis of RA 53.3% and 80%, respectively. Significant lower percentage of positivity for both AKA and IgM RF in early RA compared to late RA [p<0.01] but not for anti-CCP [p>0.05]. Patients with positive antibodies had significantly higher erosion score than those with negative ones, p<0.01 for both IgM RF and AKA and p<0.001 for anti-CCP. Anti-CCP show the highest sensitivity and specificity for RA followed by IgM RF and lastly AKA. All the studied antibodies particularly anti-CCP may help in the early diagnosis and can be considered as predictive markers for erosive articular damage in RA patients