Fluorometric assay for anti-DNA antibodies: use of ethidium bromide as intercalating dye.

Autoantibodies against double-stranded DNA in the sera of patients with various autoimmune diseases have been examined by fluorometric assay using ethidium bromide as intercalating dye. Forty-three per cent of SLE patients, 14% of SLE patients with overlapping PSS, 20% of PSS patients and none of the RA and SS patients were positive for anti-DNA antibodies. The method was found to be more sensitive than immunoprecipitation techniques and comparable with the hemagglutination assay. The technique is simple, sensitive, specific and can be employed for the detection of low concentration of anti-DNA antibodies.