Some factors affecting the quantitation of rheumatoid factors by enzyme immunoassay

Some factors affecting the use of enzyme-labelled antibody to human IgM or enzyme-labelled human IgG for the detection and assay of IgM RFs by enzyme immunoassay have been investigated. IgM RF levels, obtained by standard radioimmunoassay techniques, showed a better agreement with those obtained with enzyme-labelled antibody than with enzyme-labelled human IgG. Immuno-adsorption studies using a sheep cell agglutination test (SCAT) confirmed a partial loss of antigenicity of the IgG molecules due to glutaraldehyde treatment, which increased with the length of time of exposure to glutaraldehyde.