Efficacy and validity of automated quantitative chemiluminescent enzyme immunoassay for SARS-CoV-2 antigen test from saliva specimen in the diagnosis of COVID-19

• Published in: Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy Vol. 27; no. 7; pp. 1039 - 1042
• Main Authors: Asai, Nobuhiro, Sakanashi, Daisuke, Ohashi, Wataru, Nakamura, Akiko, Kawamoto, Yuzuka, Miyazaki, Narimi, Ohno, Tomoko, Yamada, Atsuko, Chida, Sumie, Shibata, Yuichi, Kato, Hideo, Shiota, Arufumi, Hagihara, Mao, Koita, Isao, Yamagishi, Yuka, Suematsu, Hiroyuki, Ohta, Hirotoshi, Mikamo, Hiroshige
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01-07-2021; Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd
• Subjects: COVID-19; Original; Quantitative chemiluminescent enzyme immunoassay; RT-PCR; Saliva; SARS-CoV-2; Quantitative chemiluminescent enzyme immunoassay; COVID-19; SARS-CoV-2; Saliva; RT-PCR
• ISSN: 1341-321X; 1437-7780
• DOI: 10.1016/j.jiac.2021.03.021

The pandemic of a novel coronavirus disease 2019 (COVID-19) caused by a severe acute respiratory coronavirus 2 (SARS-CoV-2) infection has been problematic worldwide. A new SARS-CoV-2 antigen test (LUMIPULSEⓇ) was licensed and widely used in Japan since May 2020. We conducted this study intending to whether the automated quantitative CLEIA antigen test using a saliva sample is effective and valid for the diagnosis of COVID-19.
We analyzed and compared the diagnostic accuracy of both the automated quantitative CLEIA antigen test and real-time RT-PCR (rRT-PCR) using a saliva sample from individuals suspected as having COVID-19.
A total of 305 samples were collected and tested in Aichi Medical University Hospital and affiliated facilities from December 2020 until January 2021 at our institute. Using reverse-transcription PCR as a reference, the AUROC of the automated quantitative CLEIA antigen test was 0.903 (95% confidential interval 0.845–0.962, p < 0.001). The appropriate cut-off antigen level was 4.0 pg/mL and had a sensitivity of 77.8%, a specificity of 99.6%, a positive predictive value of 98%, and a negative predictive value of 94.5%. On the other hand, the diagnostic accuracy of the antigen test decreased among patients among patients with COVID-19 with threshold cycle (Ct-value)≥27, which shows the AUROC was 0.795 (95%CI 0.687–0.907, p < 0.001).
While the automated quantitative CLEIA antigen test from saliva specimen could be one of the most useful diagnostic tests for the diagnosis of COVID-19 in general practice, clinicians should know the limitations of the antigen test.