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. 2023 Jun;29(6):586-591.
doi: 10.1016/j.jiac.2023.02.011. Epub 2023 Feb 26.

Evaluation of an immunochromatography-based rapid antigen test, Inspecter Kowa® SARS-CoV-2, using saliva specimens for the detection of SARS-CoV-2

Masahiro Kodana  1 , Yuta Orihara  2 , Mariko Tezuka  2 , Rina Takahashi  2 , Sakiko Noguchi  2 , Nanako Matsuzaki  2 , Tomohito Takada  2 , Naomi Kobari  2 , Kana Ogane  2 , Rieko Kawamura  2 , Toru Kawamura  2 , Shinichi Takeuchi  2 , Yuki Kamiyama  3 , Rie Shiomi  3 , Ryutaro Aoyagi  3 , Masaya Saito  3 , Takeru Kusano  3 , Nobuaki Nakaya  3 , Satoru Kaneko  4 , Hideo Morita  5 , Yoshihito Uchida  6 , Hiroaki Yazawa  7 , Ryu Sekiya  8 , Kazuki Katayama  8 , Shingo Mikami  9 , Tomoya Sato  10 , Norihito Tarumoto  11 , Takehito Kobayashi  3 , Hidetomo Nakamoto  3 , Takuya Maeda  2
Affiliations

Evaluation of an immunochromatography-based rapid antigen test, Inspecter Kowa® SARS-CoV-2, using saliva specimens for the detection of SARS-CoV-2

Masahiro Kodana et al. J Infect Chemother. 2023 Jun.

Abstract

Background: In the context of the coronavirus disease 2019 (COVID-19) pandemic, a rapid and reliable point-of-care test is an essential tool for controlling the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In particular, an immunochromatography test (ICT) that uses saliva specimens for rapid antigen detection not only reduces the risk of secondary infections but also reduces the burden on medical personnel.

Methods: The newly developed salivary antigen test kit "Inspecter Kowa® SARS-CoV-2" is an ICT to which saliva specimens can be directly applied. We evaluated its usefulness in comparison with reverse transcription quantitative PCR (RT-qPCR) and the Espline® SARS-CoV-2 Kit for the detection of SARS-CoV-2 using nasopharyngeal swab specimens. In this study, 140 patients with suspected symptomatic COVID-19 who visited our hospital were enrolled, and nasopharyngeal swab and saliva specimens were collected after they consented to participate in the study.

Results: Inspector Kowa SARS-CoV-2 was positive in 45 of 61 (73.8%) saliva that were positive by RT-qPCR and the Espline® SARS-CoV-2 Kit was also positive in 56 of 60 (93.3%) Np swabs that were positive by RT-qPCR. Good antigen detection was achieved by ICT with saliva and nasopharyngeal swab specimens when viral load was ≥105 copies/mL, whereas detection sensitivity was low when viral load was <105 copies/mL, especially in saliva specimens.

Conclusion: This ICT for the detection of SARS-CoV-2 salivary antigen is an attractive tool that does not require specialized equipment and allows patients to perform the entire process from sample collection to self-diagnose and to reduce the burden on medical care during a pandemic.

Keywords: Antigen detection; COVID-19; Immunochromatography; SARS-CoV-2; Saliva.

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Conflict of interest statement

Declaration of competing interest None.

Figures

Fig. 1
Fig. 1
Flow chart summarizing the study design. Initially, 179 patients were enrolled, but 39 were excluded due to insufficient sample volume, leaving 140 patients for the analysis.
Fig. 2
Fig. 2
Correlation of viral load analyzed using RT-qPCR between saliva and Np swab specimens.
Fig. 3
Fig. 3
Box-and-whisker plot of SARS-CoV-2 levels in saliva and Np swab specimens. The results for SARS-CoV-2 antigen-positive (Ag+)/RT-PCR-positive (PCR+) and SARS-CoV-2 antigen-negative (Ag−)/RT-PCR-positive (PCR+) samples were plotted.
Fig. 4
Fig. 4
Histograms of SARS-CoV-2 viral load in each specimen.
See this image and copyright information in PMC

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