TY - JOUR AU - Viriyataveekul, Ronnachai AU - Kobkitjaroen, Jaruda PY - 2019/05/23 Y2 - 2024/03/28 TI - Detection of Specific Autoantibodies in Sera with Negative Antinuclear Antibody by Indirect Immunofluorescence Assay but Positive by Enzyme Immunoassay JF - Siriraj Medical Journal JA - Siriraj Med J VL - 71 IS - 3 SE - Original Article DO - 10.33192/Smj.2019.36 UR - https://he02.tci-thaijo.org/index.php/sirirajmedj/article/view/190698 SP - 234-239 AB - <p><strong>Objective:</strong> The aim of this study was to investigate the predictive value of positive enzyme immunoassay (EIA) for&nbsp;detection of specific autoantibodies in sera negative for antinuclear antibody (ANA) by indirect immunofluorescence&nbsp;(IIF) assay, but positive for ANA by EIA.<br><strong>Methods:</strong> Eighty sera that tested negative for ANA by IIF, but positive for ANA by EIA were included. All sera&nbsp;were tested for specific autoantibodies by line immunoassay (LIA). The positive predictive value (PPV) of EIA was&nbsp;calculated using LIA result as a reference standard. Medical records of patients were reviewed. Clinical findings at<br>the time of blood sampling for ANA testing and at 5 years after sampling were obtained.<br><strong>Results:</strong> Twenty-eight sera (35%) were found to be positive by LIA. The PPV of EIA for detection of specific&nbsp;autoantibodies at the manufacturer’s recommended cut-off was 35.0% (95% CI: 24.5-45.5%). The most prevalent&nbsp;antibodies were anti-SSA/Ro60 (64.3%, 95% CI: 46.5-82.0%), anti-Ro52 (25.0%, 95% CI: 9.0-41.0%), and anti-SSB/<br>La (10.7%, 95% CI: 0-22.2%). A diagnosis of systemic autoimmune rheumatic disease was established in 7 patients&nbsp;(25%) at the time of blood sampling, and 4 patients (14.3%) were diagnosed with non-rheumatic autoimmune disease.<br><strong>Conclusion:</strong> EIA testing in IIF-ANA negative sera yielded a chance to detect antinuclear antibodies. However, the&nbsp;poor PPV of EIA may have low benefit in real-life clinical practice. Anti-SSA/Ro60 was the most prevalent antibody&nbsp;detected. A high proportion of LIA-ANA positive patients were not diagnosed as autoimmune disease at the time&nbsp;of antibody detection.</p> ER -