BMC Medicine (Oct 2022)

Head-to-head comparison of the accuracy of saliva and nasal rapid antigen SARS-CoV-2 self-testing: cross-sectional study

  • Ewoud Schuit,
  • Roderick P. Venekamp,
  • Irene K. Veldhuijzen,
  • Wouter van den Bijllaardt,
  • Suzan D. Pas,
  • Joep J. J. M. Stohr,
  • Esther B. Lodder,
  • Marloes Hellwich,
  • Richard Molenkamp,
  • Zsofia Igloi,
  • Constantijn Wijers,
  • Irene H. Vroom,
  • Carla R. S. Nagel-Imming,
  • Wanda G. H. Han,
  • Jan A. J. W. Kluytmans,
  • Susan van den Hof,
  • Janneke H. H. M. van de Wijgert,
  • Karel G. M. Moons

DOI
https://doi.org/10.1186/s12916-022-02603-x
Journal volume & issue
Vol. 20, no. 1
pp. 1 – 14

Abstract

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Abstract Background The diagnostic accuracy of unsupervised self-testing with rapid antigen diagnostic tests (Ag-RDTs) is mostly unknown. We studied the diagnostic accuracy of a self-performed SARS-CoV-2 saliva and nasal Ag-RDT in the general population. Methods This large cross-sectional study consecutively included unselected individuals aged $$\ge$$ ≥ 16 years presenting for SARS-CoV-2 testing at three public health service test sites. Participants underwent molecular test sampling and received two self-tests (the Hangzhou AllTest Biotech saliva self-test and the SD Biosensor nasal self-test by Roche Diagnostics) to perform themselves at home. Diagnostic accuracy of both self-tests was assessed with molecular testing as reference. Results Out of 2819 participants, 6.5% had a positive molecular test. Overall sensitivities were 46.7% (39.3–54.2%) for the saliva Ag-RDT and 68.9% (61.6–75.6%) for the nasal Ag-RDT. With a viral load cut-off (≥ 5.2 log10 SARS-CoV-2 E-gene copies/mL) as a proxy of infectiousness, these sensitivities increased to 54.9% (46.4–63.3%) and 83.9% (76.9–89.5%), respectively. For the nasal Ag-RDT, sensitivities were 78.5% (71.1–84.8%) and 22.6% (9.6–41.1%) in those symptomatic and asymptomatic at the time of sampling, which increased to 90.4% (83.8–94.9%) and 38.9% (17.3–64.3%) after applying the viral load cut-off. In those with and without prior SARS-CoV-2 infection, sensitivities were 36.8% (16.3–61.6%) and 72.7% (65.1–79.4%). Specificities were > 99% and > 99%, positive predictive values > 70% and > 90%, and negative predictive values > 95% and > 95%, for the saliva and nasal Ag-RDT, respectively, in most analyses. Most participants considered the self-performing and result interpretation (very) easy for both self-tests. Conclusions The Hangzhou AllTest Biotech saliva self Ag-RDT is not reliable for SARS-CoV-2 detection, overall, and in all studied subgroups. The SD Biosensor nasal self Ag-RDT had high sensitivity in individuals with symptoms and in those without prior SARS-CoV-2 infection but low sensitivity in asymptomatic individuals and those with a prior SARS-CoV-2 infection which warrants further investigation.

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