Evaluati̇on of antinuclear antibody screen tests on diagnosis of autoimmune diseases

Anti nuclear antibodies (ANA) has critical role for diagnosis of autoimmune diseases. Acording to algortihm for serodiagnosis, a screen test such as indirect immunofluorescence (IIF) test on Hep-2 cells or screen enzyme-linked immunosorbent assay (ELISA) is used, in case of positive result, then, generally immunoblot (e.g. line blot [LB]) or ELISA using extractable nuclear antigens is tested to detect responsible antibody. Although IIF test is accepted gold standard as a screen test, it has some troubles which are needing expertise, and has subjectivity and lack of standartisation. Although , it has been reported that ELISA is an alternative screen test produce good agreement with IIF test, it also has limitations to detect antibodies. In this study we aimed to reveal results of IIF test using for diagnosis on autoimmune disease as multicenter for the first time and to determine the efficiency of ELISA. Total 600 sera which were known that consist of 287 positive of LB and 313 negatif of both IFAT and LB that had storaged suitable condition tested for IIF test in Hospital of Celal Bayar University. Tests were studied at 1/100 dilution and evaluated with double blind method by four centers which are university hospital giving third step medical services at the same area. Diagnosis of patterns and fluorescence intensity were compare with each other and LB test. Sixty five of 600 sera had removed for ELISA test because of that LB test had results which ELISA couldn't identify them, so 535 sera tested by ANA screen ELISA kit screening 10 antibodies on automated ELISA analyzer. 55 The agreement which was ignored patterns between LB test and IIF test results of centers had found 81.8%, 80.0%, 79,8% and 78.7% for Center 1, 2, 3 and 4 respectively, Agreement regarding patterns between positive results were relatively low, 54.4%, 49.8%, 44.9% and 60.0% respectively and overall agreement include negative results were 70.8%, 72.2%, 69.0%, 64.0%, respectively. Agreement among four centers were seen at 392 results (65.3%), but it was only 39.3% in positive results. Agreement of fluorescence intensity reported as semi-quantitative,3+, maximum, in IIF test were found the highest at (3+) level. Of 87 in consistent 100 results among the four centers were at (3+) level. and of these 73 sera had agreement with LB test. Of ANA screen ELISA test, 148 (66.7%) positive and 303 (96.8%) negative results were agreement with LB, and overall agremeent was 84.3%. In conclusion; evaluation of patterns was lower than expected for agreement on LB and IIF test. Agreement of four centers in knowing of patterns and fluorescence intentisy was satsfactory in high titer. Although ELISA had high agreement in negative results, but was lower agreement than IIF test in positive sera for two centers. Results of ELISA and IFAT patterns had weak performance at low antibody titers for serodiagnosis of autoimmune diseseas Key words: Autoimmune disease, indirect immunofluorescence test, ELISA, pattern.