Differential effects of therapeutic regimens on specific classes of rheumatoid factor.

This study was performed to define further the relationship of circulating IgM and IgG rheumatoid factor to the articular manifestations of rheumatoid arthritis. Patients with substantial clinical improvement (greater than 55%) or no improvement or worsening were chosen for study. Patients were further selected to include those treated with non-steroidal anti-inflammatory drugs (NSAIDs) alone, or NSAIDs plus D-penicillamine or gold. Significant reductions of IgM (p less than 0.001) and IgG (p less than 0.005) rheumatoid factor were seen only in those treated with gold who improved clinically. These observations suggest that in patients experiencing comparable degrees of clinical improvement the simultaneous alterations of circulating IgG and IgM rheumatoid factor observed are dependent upon the therapeutic regimen employed.