Comparison of rheumatoid factor of IgM, IgG, and IgA isotypes with disease activity score 28 in patients of rheumatoid arthritis

Abstract

Sana Zainab, Muhammad Kashif, Romeeza Tahir, Faheem Shahzad, Aflak Rasheed, Waqas Latif,Tafazzul H. Mahmud, Nadeem Afzal

Background/Objectives: For the diagnosis of rheumatoid arthritis (RA), rheumatoid factor (RF) is a commonly used serological marker. Almost two-third of patients with RA have RF in their serum and it is associated with disease activity, bone erosion, and disease outcome. RF is an autoantibody targeting the “fraction crystallizable” (Fc) region of IgG antibodies and exists as IgA, IgG, and IgM isotypes. Subjects and Methods: The current study was aimed to compare the RF isotypes IgM, IgG, and IgA with disease activity score (DAS) 28 in RA patients. This was a descriptive study, which included 83 RA patients. Blood samples of the patients were collected from the Department of Rheumatology, Sheikh Zayed Hospital Lahore. The levels of different isotypes of RF, i.e., IgM, IgG, and IgA were determined by enzyme linked immunosorbent essay technique. Data were analyzed by SPSS 20.0. Results: RF isotypes IgM, IgG, and IgA were detected in 83%, 10%, and 40% of RA patients, respectively. RF isotypes were compared with DAS 28. No significant association was noticed between DAS 28 and RF IgM {Odd ratio (OR) [confidence interval (CI)]} [0.5 (0.07–3.18)], RF IgG [3.0 (0.27–32.20)], and RF IgA [0.4 (0.43–0.13)]. Disease duration was also compared with RF isotypes. There was no significant association between disease duration and RF IgM [OR (CI)] [1.4 (0.46–4.86)], RF IgG [1.6 (0.50–5.0)], and RF IgA [1.1 (0.53–2.7)]. All the isotypes of RF were detected in RA patients. Conclusion: All the isotypes of RF were detected in RA patients. IgM-RF is superior to other RF isotypes as a screening method for RA