Routine assay for detection of IgG and IgM antiglobulins in seronegative and seropositive rheumatoid arthritis.

A convenient technique suitable for the routine estimation of IgM and IgG antiglobulins has been devised. The assay involves the binding of antiglobulins (rheumatoid factors) to rabbit immunoglobulin linked to the surface of plastic tubes; the amount of antiglobulin bound is then determined by adding radiolabelled antihuman IgG or IgM. Both antiglobulins were raised in virtually all seropositive rheumatoid arthritics, and 19 out of 22 seronegative patients had raised values for either IgM or IgG rheumatoid factors. The test should prove valuable in diagnosis and the results further emphasize autosensitization to IgG as a dominant immunological characteristic of different forms of rheumatoid arthritis.