Relationship of rheumatoid factor isotype levels with joint lesions detected by magnetic resonance imaging in early rheumatoid arthritis

Objective. To evaluate the relationship between rheumatoid factor isotypes and articular damage detected by magnetic resonance imaging and plain radio graphy in early rheumatoid arthritis. Methods. 20 consecutive patients with early active rheumatoid arthritis underwent determinations of serum IgM, I gA, and IgG rheumatoid factors by enzyme-linked immunosorbent assay (ELISA) . Plain radiographs of the hands and wrists were obtained, and the wrist, m etacarpophalangeal joints, and proximal interphalangeal (PIP) joints on the more severely affected side were investigated by magnetic resonance imagin g before and after gadolinium-DTPA injection. Results. IgM, IgA, and IgG rh eumatoid factors were found in 13 (65%), 13 (65%), and 15 (75%) of patients , respectively. Sera from five patients (25%) contained no detectable rheum atoid factor isotypes. Correlations were found among the levels of the thre e rheumatoid factor isotypes. Levels of IgA, IgG, and IgM rheumatoid factor were significantly higher in patients with than without erosions on magnet ic resonance imaging scans. No such difference was found when patients with and without erosions on plain radiographs were compared. Magnetic resonanc e imaging detected soft tissue lesions more frequently than plain radiograp hy. Magnetic resonance imaging was also more likely than plain radiography to show bone erosions and bone cysts, but this difference was not statistic ally significant. Conclusions. Quantitative rheumatoid factor isotype assay s and magnetic resonance imaging evaluation of erosions of the hand and wri st may be useful for investigating patients with early rheumatoid arthritis .