Five-Year Analysis of Anti-Nuclear Antibody (ANA) and Extractable Nuclear Antigen Antibody (anti-ENA) Immunoblot Test Results

Abstract

Autoimmune disorders may cause systemic disease in which multiple organs are affected or may also be localized as single-organ involvement. Various ancillary immunological tests used in cases where systemic involvement is observed, and differential diagnosis becomes difficult or non-specific symptoms are observed. For this purpose, investigation of antinuclear antibodies (ANA) and antibodies against extractable nuclear antigens (ENA) in patient serums using various methods is a guide for clinicians. In this study, we aimed to evaluate the effectiveness of ANA and ENA antibody tests by examining the test results, the patients’ demographic data, and the clinics that ordered the tests. In the study, a retrospective review of the results of 37,791 ANA tests studied on serum samples sent to the medical microbiology laboratory of our hospital from various clinics between January 2018 and December 2022 is presented. ANA tests were resulted semi-quantitatively by evaluating the slides prepared using diluted serum samples at a ratio of 1:100 and HEp-2 cells and monkey liver tissue under a fluorescent microscope with the indirect immunofluorescence (IIF) antibody method. Of the patients who requested ANA test, 11,604 (30.7%) were male and 26,187 (69.3%) were female. The mean ages were 43.46 (0-94) and 46.94 (0-96), respectively. Of the samples tested, 18.8% (7,107/37,791) were evaluated as ANA positive. The ANA positivity rate was significantly higher in women (24.8%) than in men (19.7%) (p<0.001). ANA positive samples were re-tested using the anti-ENA immunoblot method. Of the 7,107 ANA-positive patients, 3,809 (53.6%) were found to be anti-ENA positive for at least one specific antibody, while 3,298 (46.4%) were negative. In the anti-ENA profile, antibodies against 11 different antigen types were screened and the most frequently detected antibody was anti-SS-A (22.7%), and this was followed by anti-centromere (12.8%), anti-RNP (10.2%), and anti-dsDNA (9.7%) antibodies. Immunoblot-based anti-ENA tests provide specific information for the diagnosis of autoimmune diseases. In our study, the fact that anti-ENA tests were negative in a significant part of ANA positive patients indicates the inadequacy of the immunoblot test panel and reveals the need for immunoblot tests with wider antibody diversity or any alternative methods.