Significance of discrepant results for dsDNA antibody by radioimmunoassay and immunofluorescence

Abstract

The presence of antibodies to double-stranded DNA (dsDNA) constitutes one of the American Rheumatism Association (ARA) 1982 revised criteria for the diagnosis of systemic lupus erythematosus (SLE). This study was designed to follow up all patients for whom the dsDNA antibody results were discrepant when assayed by radioimmunoassay (RAI) and immunofluorescence (IF). 1157 samples were assayed; of these 1048 were double negative, 59 double positive, 30 positive by IF only and 20 positive by RIA only. Information on the presence of the other ARA criteria for SLE were available for 42 patients. If the single positive test was considered to be a false positive result, only 5 of the 42 patients met the ARA criteria for SLE. However, if the single positive test by either method was considered to be a true positive then 15 of the 42 patients satisfied the criteria for SLE. Eighteen patients were RIA positive/IF negative and of these 11 satisfied the criteria for SLE and 7 did not. Conversely 24 patients were RIA negative/IF positive and of these only 4 satisfied the criteria for SLE while 20 did not. It was concluded that when discrepant results were obtained for dsDNA antibodies, particularly if negative by RIA, then the results should be given a lower weighting as a criteria for SLE.