PLoS ONE (Jan 2021)

An optimized stepwise algorithm combining rapid antigen and RT-qPCR for screening of COVID-19 patients.

  • Philippe Halfon,
  • Guillaume Penaranda,
  • Hacène Khiri,
  • Vincent Garcia,
  • Hortense Drouet,
  • Patrick Philibert,
  • Christina Psomas,
  • Marion Delord,
  • Frédérique Retornaz,
  • Caroline Charpin,
  • Thomas Gonzales,
  • Hervé Pegliasco,
  • Jérôme Allardet-Servent

DOI
https://doi.org/10.1371/journal.pone.0257817
Journal volume & issue
Vol. 16, no. 9
p. e0257817

Abstract

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Background & aimWe investigated the combination of rapid antigen detection (RAD) and RT-qPCR assays in a stepwise procedure to optimize the detection of COVID-19.MethodsFrom August 2020 to November 2020, 43,399 patients were screened in our laboratory for COVID-19 diagnostic by RT-qPCR using nasopharyngeal swab. Overall, 4,691 of the 43,399 were found to be positive, and 200 were retrieved for RAD testing allowing comparison of diagnostic accuracy between RAD and RT-qPCR. Cycle threshold (Ct) and time from symptoms onset (TSO) were included as covariates.ResultsThe overall sensitivity, specificity, PPV, NPV, LR-, and LR+ of RAD compared with RT-qPCR were 72% (95%CI 62%-81%), 99% (95% CI95%-100%), 99% (95%CI 93%-100%), and 78% (95%CI 70%-85%), 0.28 (95%CI 0.21-0.39), and 72 (95%CI 10-208) respectively. Sensitivity was higher for patients with Ct ≤ 25 regardless of TSO: TSO ≤ 4 days 92% (95%CI 75%-99%), TSO > 4 days 100% (95%CI 54%-100%), and asymptomatic 100% (95%CI 78-100%). Overall, combining RAD and RT-qPCR would allow reducing from only 4% the number of RT-qPCR needed.ConclusionsThis study highlights the risk of misdiagnosing COVID-19 in 28% of patients if RAD is used alone. A stepwise analysis that combines RAD and RT-qPCR would be an efficient screening procedure for COVID-19 detection and may facilitate the control of the outbreak.