Analytical performance of the rapid qualitative antigen kit for the detection of SARS-CoV-2 during widespread circulation of the Omicron variant

J Infect Chemother. 2023 Mar;29(3):257-262. doi: 10.1016/j.jiac.2022.11.006. Epub 2022 Nov 20.


Introduction: Rapid qualitative antigen testing is essential in the clinical management of COVID-19. However, most evaluations of antigen tests have been performed before the emergence of the Omicron variant.

Methods: This prospective observational study evaluated QuickNavi-COVID19 Ag, a rapid antigen detection test between December 2021 and February 2022 in Japan, using real-time reverse transcription (RT)-PCR as a reference. Two nasopharyngeal samples were simultaneously collected for antigen testing and for RT-PCR. Variant analysis of the SARS-CoV-2 genomic sequencing was also performed.

Results: In total, nasopharyngeal samples were collected from 1073 participants (417 positive; 919 symptomatic; 154 asymptomatic) for analysis. Compared with those of RT-PCR, the sensitivity, specificity, positive predictive value, and negative predictive value were 94.2% (95% CI: 91.6%-96.3%), 99.5% (95% CI: 98.7%-99.9%), 99.2% (95% CI: 97.8%-99.8%), and 96.5% (95% CI: 94.8%-97.7%), respectively. The sensitivity among symptomatic individuals was 94.3% (95% CI: 91.5%-96.4%). Overall, 85.9% of sequences were classified as Omicron sublineage BA.1, 12.4% were Omicron sublineage BA.2, and 1.6% were Delta B.1.617.2. (Delta variant). Most of the samples (87.1%) had Ct values of <25, and the sensitivity was 47.4% for low viral load samples (Ct ≥ 30); a similar trend has been observed in both symptomatic and asymptomatic groups.

Conclusions: The QuickNavi-COVID19 Ag test showed sufficient diagnostic performance for the detection of the SARS-CoV-2 Omicron sublineages BA.1 and BA.2 from nasopharyngeal samples. However, the current study was mainly performed in symptomatic patients and the results are not sufficiently applicable for asymptomatic patients.

Keywords: COVID-19; Nasopharyngeal sample; Omicron variant; QuickNavi-COVID19 Ag; SARS-CoV-2.

Publication types

  • Observational Study

MeSH terms

  • COVID-19* / diagnosis
  • Humans
  • Japan
  • Real-Time Polymerase Chain Reaction
  • SARS-CoV-2* / genetics
  • Sensitivity and Specificity

Supplementary concepts

  • SARS-CoV-2 variants