Prospective study of three saliva qualitative antigen testing kits for the detection of SARS-CoV-2 among mainly symptomatic patients in Japan

J Infect Chemother. 2023 Jul;29(7):654-659. doi: 10.1016/j.jiac.2023.03.005. Epub 2023 Mar 7.


Introduction: Rapid qualitative antigen testing has been widely used for the laboratory diagnosis of COVID-19 with nasopharyngeal samples. Saliva samples have been used as alternative samples, but the analytical performance of those samples for qualitative antigen testing has not been sufficiently evaluated.

Methods: A prospective observational study evaluated the analytical performance of three In Vitro Diagnostics (IVD) approved COVID-19 rapid antigen detection kits for saliva between June 2022 and July 2022 in Japan using real-time reverse transcription polymerase chain reaction (RT-qPCR) as a reference. A nasopharyngeal sample and a saliva sample were simultaneously obtained, and RT-qPCR was performed.

Results: In total, saliva samples and nasopharyngeal samples were collected from 471 individuals (RT-qPCR-positive, n = 145) for the analysis. Of these, 96.6% were symptomatic. The median copy numbers were 1.7 × 106 copies/mL for saliva samples and 1.2 × 108 copies/mL for nasopharyngeal samples (p < 0.001). Compared with the reference, the sensitivity and specificity were 44.8% and 99.7% for ImunoAce SARS-CoV-2 Saliva, 57.2% and 99.1% for Espline SARS-CoV-2 N, and 60.0% and 99.1% for QuickChaser Auto SARS-CoV-2, respectively. The sensitivities of all antigen testing kit were 100% for saliva samples with a high viral load (>107 copies/mL), whereas the sensitivities were <70% for high-viral-load nasopharyngeal samples (>107 copies/mL).

Conclusion: COVID-19 rapid antigen detection kits with saliva showed high specificity, but the sensitivity varied among kits, and were also insufficient for the detection of symptomatic COVID-19 patients.

Keywords: COVID-19; Qualitative antigen testing; SARS-CoV-2; Saliva sample.

Publication types

  • Observational Study

MeSH terms

  • COVID-19* / diagnosis
  • Humans
  • Japan
  • Nasopharynx
  • Prospective Studies
  • SARS-CoV-2*
  • Saliva
  • Sensitivity and Specificity
  • Specimen Handling