Evaluation of the rheumatoid factors of the IgG, IgM and IgA isotypes as prognostic parameters for rheumatoid arthritis among Iraqi patients

Context: Rheumatoid arthritis (RA) has a heterogeneous course, spanning from mild forms tending to remission and reacting well to treatment, to aggressive forms resistant to classical therapeutic measures. Reliable predictive parameters of the disease course in RA are needed. Raised levels of Rheumatoid Factors (RFs) are associated with RA and that this RF is found in IgM, IgA and IgG classes (isotypes). Aims: To figure out the value of RF isotypes titers as predictors for RA processes and outcomes. Materials and Methods: Fifty three RA patients were enrolled in this study. The patients were diagnosed based on ACR criteria. Blood sample was taken from each patient at time of attending; sera were separated immediately and kept frozen at -70 degrees C until used. Disease Activity Score (DAS) was calculated using DAS28-3 formula. Radiographs were read by expert radiologists. Sandwich Enzyme-linked Immunosorbent Assay (ELISA) was used for the separate quantitative detection of RF of the IgG, IgM and IgA classes in serum. Statistical Analysis Used: Chi-square, Pearson's correlation coefficient and ROC statistical analyses was performed using SPSS version 15.0. Results: Among the 53 RA patients who were enrolled in this study, there were statistically significant positive correlations between the presence of radiological joint changes with serum levels of IgG-RF, IgM-RF and IgA-RF as measured by calculation of area under curve (0.772, 0.703 and 0.769, respectively). However, no correlation could be found between those RF isotypes with any of other disease processes and outcomes. Conclusions: These results may indicate the importance of the titers of those isotypes as good predictors of erosive RA and may reflect a causal relationship between their titers and joint damage during the course of RA.