Assessment of the Impact of Anti-nuclear Antibody (ANA) Titer and Pattern on Anti-extractable Nuclear Antigen (ENA) Positivity: Experience at Cheikh Khalifa Hospital.

This retrospective study examined the relationship between anti-nuclear antibody (ANA) titers, immunofluorescence (IIF) patterns, demographic variables, and anti-extractable nuclear antigen (ENA) positivity in a cohort of 538 patients at Cheikh Khalifa Hospital. Among them, 409 of 538 patients (76%) were women, and 129 of 538 (24%) were men. ANA and 15 ENA specificities were assessed using indirect IIF on Hep-2/monkey liver substrates and immunoblot analysis with the ANA Profile 3 Plus DFS-70 kit (EUROIMMUN Medizinische Labordiagnostika AG, Lübeck, Germany). ANA staining patterns were classified based on ICAP guidelines as speckled (S-ANA), homogeneous (H-ANA), cytoplasmic (C-ANA), and nucleolar (N-ANA). Certain patterns are known to be associated with specific antibodies or clinical conditions; for example, S-ANA may suggest anti-Sm antibodies in systemic lupus erythematosus, while C-ANA is often linked to anti-mitochondrial or anti-Jo-1 antibodies, commonly seen in primary biliary cholangitis or antisynthetase syndrome, respectively. Chi-square analyses were used to identify key factors predictive of ENA positivity. ANA was detected in 326 of 538 patients (60%). Among those who were positive, most were S-ANA, observed in 161 of 326 patients (49%). The second most common pattern was H-ANA, found in 49 of 326 (15%). Anti-ENA antibodies were identified in 268 of 538 patients (50%), with Ro-52, SS-A, and Pm-Scl100 being the most commonly detected specificities. Moderate and higher ANA titers (≥1:320) showed a strong association with ENA positivity. Our analyses indicate that high ANA titers and specific patterns, particularly S-ANA and H-ANA, are associated with ENA positivity and may aid in the interpretation of ENA tests. We also found that C-ANA didn't show any predictive value for ENA positivity. In contrast, N-ANA did have some predictive value but less unequivocal relationships with some ENA antibodies. The study noted that more women and patients aged 40-60 showed positive anti-ENA results; however, these observations may be affected by the overrepresentation of these groups. Furthermore, 47 of 538 patients (9%) who tested negative for ANA were still found to be anti-ENA positive, highlighting discrepancies that can occur between detection methods. These findings underscore the importance of integrating ANA profiles with the patient's clinical context, including their medical history and examination findings, to enhance diagnostic precision. Moving forward, further studies with standardized assay procedures and prospective clinical follow-up would help refine the interpretation of serological results.