Antinuclear antibody determination methods.

Screening rheumatology patients for anti-nuclear and anti-cytoplasmic antibodies is easily done in a qualitative manner using the IF, CIE and ID assays. The immunoblot is of use for anti-La and anti-RNP assays but gives anomalous results for Sm binding by anti-RNP sera and is not easily quantitated. These deficiencies of the immunoblot do not apply to the ELISA. Advances in cloning of autoantigens will enable standardisation of antigen preparations used for these ELISAs. The quantitation of autoantibody appears significant since disease flares occur together with elevations in specific autoantibody. IgM anti-Sm autoantibody was detected with a different disease distribution to IgG anti-Sm but the prognostic implications for this remain to be determined.