A new assay for rheumatoid factor

This solid-phase immunoassay for detection of rheumatoid factor involves a specially prepared indium surface that renders protein layers visible and therefore does not require tagged protein. Using appropriate discriminatory values, we found agreement with results of a standard latex-fixation test in controls and patients with rheumatoid arthritis. About half of the patients with rheumatoid arthritis that were seronegative by this latex fixation test had positive tests by the present assay. Rheumatoid factor of both the IgM and IgA class may be easily assessed.