Comparison of the methods used for the detection of antinuclear antibodies

The production of one or more autoantibodies in the majority of rheumatic diseases is a common clinical finding. Indirect immunofluorescent antibody (IFA) test is the former and widely used method in detecting autoantibodies. Recently, commercial enzyme immunoassays (EIA) and immunoblot (IB) assays are available for the routine laboratories. The aim of this study was to compare the efficacies of these methods in 121 sera samples which were collected from 46 male and 75 female patients, of whom antinuclear antibody (ANA) testing were requested by clinicians. All the samples were simultaneously studied by IFA with HEp-2 and Crithidia lucillae cells, and by two different commercial kits of EIA and IB, and the results were evaluated. When IFA is accepted as reference method, the sensitivities and specificities of the other methods were found as follows, respectively; 82-100% and 84-100% for ANA-EIA, 48-54% and 98-100% for ANA-IB, 66-100% and 97-98% for anti-dsDNA-EIA, and 50-66% and 86-100% for anti-dsDNA-IB. The agreement rates of ANA-EIA, ANA-IB, anti-dsDNA-EIA and anti-dsDNA-IB methods with IFA were detected as 82-90%, 74%, 96-97%, and 84-98%, respectively. As a result, it may be concluded that IFA test should be used as a primarily test for the detection of ANA and anti-dsDNA autoantibodies, while EIA and IB methods are useful for antigen differentiation and confirmation of the results.