Article in Japanese

Evaluating the relationship between RS virus infections and “indeterminable” SARS-CoV-2 antigen quantitative test results

Kenichiro SUGIYAMA^{1, 2）}, Yoshiki KUSAMA^1～3）, Takateru IHARA^{1, 2）}, Yusuke ITO^{1, 4）}, Katsunori KAMIMURA^{1, 2）}, Toshiro MAIHARA^1）

The number of patients in our facility who had “indeterminable” results on the SARS-CoV-2 antigen quantitative test increased during the respiratory syncytial virus (RSV) epidemic. Thus, we hypothesized that RSV infection increases the number of “indeterminable” in SARS-CoV-2 antigen quantitative test. To test this hypothesis, we investigated the relationship between RSV and the SARS-CoV-2 antigen quantitative test. From January 2022 to December 2022, we assessed patients under the age of 15 who underwent examinations in our hospital. Specifically, we focused on patients whose SARS-CoV-2 antigen test results were either “negative” or “indeterminable”. We calculated the odds ratio using logistic regression, binary objective variables of “indeterminable” and “negative,” and an explanatory variable of “RSV infection.” Furthermore, we included “month age” and “tests performed during months with a higher number of submissions” as explanatory variables and conducted a multivariable analysis. We identified 29 cases of “indeterminable” samples and 175 cases of “negative” samples. RSV infection was a significant factor of “indeterminable” samples in univariate analysis (OR 2.96, 95% CI: 1.10-7.93); however, it became non-significant in multivariate analysis (aOR 2.03, 0.71-5.81). Conversely, “tests performed during months with a higher number of submissions” became a significant factor of “indeterminable” samples (aOR 4.34, 1.24-15.14). In addition, the quantity of test submissions and that of “indeterminable” samples were strongly correlated (R=0.85, 0.54-0.96). These findings imply that an increase in “indeterminable” samples in SARS-CoV-2 antigen quantitative tests could be a result of the increased test submissions, rather than increased incidence of RSV infections.

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1）Department of Pediatrics, Hyogo Prefectural Amagasaki Medical Center
2）Division of General Pediatrics, Hyogo Prefectural Amagasaki Medical Center
3）Prevention, Graduate School of Medicine / Faculty of Medicine, Osaka University
4）Division of Pediatric Infectious Diseases, Hyogo Prefectural Amagasaki Medical Center

Key words	RSvirus infection, SARS-CoV-2, antigen quantitative test, indeterminable
Received	December 23, 2023
Accepted	March 13, 2024

36 (2)：119─125,2024