{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,9,24]],"date-time":"2025-09-24T06:10:12Z","timestamp":1758694212166,"version":"3.44.0"},"reference-count":31,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,9,24]],"date-time":"2025-09-24T00:00:00Z","timestamp":1758672000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Microbiol."],"abstract":"<jats:sec><jats:title>Introduction<\/jats:title><jats:p>The precise diagnosis of a prior COVID-19 infection remains challenging. This study aimed to evaluate the efficacy of T-SPOT assays for diagnosing prior SARS-CoV-2 infections by using frozen peripheral blood mononuclear cells (PBMCs) combined with antibody tests.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>The study included 122 participants with PCR-confirmed COVID-19 (the positive control cohort) and 67 participants with no evidence of prior infection (the negative control cohort). Antibody testing was conducted using iFlash-SARS-CoV-2 IgG (YHLO, iF_N) and MAGPIX<jats:sup>\u00ae<\/jats:sup> assays (Luminex, Lumi_N), which target the nucleocapsid protein. T-SPOT<jats:sup>\u00ae<\/jats:sup> Discovery SARS-CoV-2 assays (Oxford Immunotec) were used to detect cell-mediated immune responses against nucleocapsid (Tspot_N) and membrane (Tspot_M) proteins.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Antibody tests had similar sensitivities (if_N: 67.2% and Lumi_N: 64.8%) and specificities (&amp;gt;98.4%). The Tspot_N assay demonstrated comparable performance to the antibody tests, with a sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of 62.5% (95% confidence interval: 52.0%\u201372.2%), 98.4% (95% CI: 91.2%\u2013100.0%), and 0.923, respectively. The Tspot_M assay had lower sensitivity (15.3%). The combination of the Tspot_N test and the Lumi_N antibody test significantly improved the sensitivity and AUC to 88.0% and 0.979, respectively (<jats:italic>p<\/jats:italic> = 0.012). Net reclassification improvement and integrated discrimination improvement analyses further supported the improved diagnostic performance of the combination assay.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>Frozen PBMCs were useful for performing T-SPOT assays. The combination of T-SPOT assays targeting nucleocapsid protein and antibody tests improved the diagnosis of past SARS-CoV-2 infections in vaccinated participants. These findings suggest that integrating cellular and humoral immunity assays can facilitate COVID-19 prevalence studies.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fmicb.2025.1675605","type":"journal-article","created":{"date-parts":[[2025,9,24]],"date-time":"2025-09-24T05:42:13Z","timestamp":1758692533000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Improving the diagnostic performance for prior COVID-19 with T-SPOT, an interferon-gamma release assay"],"prefix":"10.3389","volume":"16","author":[{"given":"Masaki","family":"Yamamoto","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Michael T.","family":"White","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takahisa","family":"Kawaguchi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kazuya","family":"Setoh","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yusuke","family":"Tsuda","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Koh","family":"Shinohara","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yasuhiro","family":"Tsuchido","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yasufumi","family":"Matsumura","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fumihiko","family":"Matsuda","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Miki","family":"Nagao","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2025,9,24]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"920227","DOI":"10.3389\/fimmu.2022.920227","article-title":"Coordinated innate and T-cell immune responses in mild COVID-19 patients from household contacts of COVID-19 cases during the first pandemic wave.","volume":"13","author":"Aiello","year":"2022","journal-title":"Front. 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