The occurrence of rheumatoid factor isotypes in early definite rheumatoid arthritis--no relationship with erosions or disease activity

Seventy-one patients with definite rheumatoid arthritis and disease duration less than 2 years were followed prospectively. At study entry 43 patients had IgG rheumatoid factor (RF), 59, IgA-RF and 64, IgM-RF as measured with an ELISA; 48 were Waaler-Rose positive. After 2 years, joint erosions were present in 51 patients and absent in 19. One patient has not been followed long enough. The calculated relative risks contributed by different RF to the presence of erosions were low. No significant correlations between markers of disease activity and RF levels initially were found. The clinical value of RF isotype determination seems limited.