[Comparison of indirect immunofluorescence and enzyme immunoassay methods for the determination of antinuclear antibodies].

Antinuclear antibodies (ANA) are widely used for screening and monitoring of connective tissue diseases (CTD). Indirect immunofluorescence assay (IFA) is the standard method which is more often preferred for detecting these antibodies. Another method is enzyme immunoassay (ELISA) which includes extractable nuclear antigens (ENA). The aim of this study was to compare two different methods in view of their performances in the detection of ANA. A total of 27 sera from patients prediagnosed as different types of CTD, were screened by ANA-IFA (Zeus Scientific Inc, USA) and ELISA (Zeus Scientific Inc, ENA Profile-6, USA) methods. In addition, specific staining patterns of ANA on HEp-2 cells as a substrate, were enrolled with IFA. As a result, ANA positivity was detected in all of the 27 samples (100%) by IFA, and only in 7 (25.9%) by ELISA. The concordance rate between two different assays was estimated as 38.6%, and a statistically significant difference was found between the methods in the detection of ANA (x2=20, p<0.001). In conclusion, ANA-IFA method is still a reliable routine screening method for the laboratory diagnosis of CTD, while ENA Profile-6 ELISA may give false negative results, because of its limited antigen content, and should be supported with additional antigens.