A rapid enzyme immunoassay for the detection of IgM rheumatoid factor--a comparison of "sero-negative" and "sero-positive" rheumatoid patients.

The ELISA technique for measuring RF is a reliable, low cost, quick method which has adequate specificity and improved sensitivity over other methods. This last property plus its flexible potential for measuring RF in classes other than IgM should make it a particularly useful tool in assessing "sero-negative" patients, while in the long run its routine use should supersede that of the other tests.