key: cord-0687988-n642wlsx
authors: Porte, Lorena; Legarraga, Paulette; Vollrath, Valeska; Aguilera, Ximena; Munita, José M.; Araos, Rafael; Pizarro, Gabriel; Vial, Pablo; Iruretagoyena, Mirentxu; Dittrich, Sabine; Weitzel, Thomas
title: Evaluation of novel antigen-based rapid detection test for the diagnosis of SARS-CoV-2 in respiratory samples
date: 2020-06-01
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2020.05.098
sha: f3a0bd04bc43f674e28c6bfe93141110a2e430f4
doc_id: 687988
cord_uid: n642wlsx

OBJECTIVES: In the context of the Covid-19 pandemic, the development and validation of rapid and easy-to-perform diagnostic methods are of high priority. We evaluated a novel rapid antigen detection test (RDT) for SARS-CoV-2 in respiratory samples. METHODS: The fluorescence immunochromatographic SARS-CoV-2 antigen test (Bioeasy Biotechnology Co., Shenzhen, China) was evaluated using universal transport medium with nasopharyngeal (NP) and oropharyngeal (OP) swabs from suspected Covid-19 cases. Diagnostic accuracy was determined in comparison to SARS-CoV-2 real time (RT)-PCR. RESULTS: A total of 127 samples were included; 82 were RT-PCR positive. Median patients’ age was 38 years, 53.5% were male, and 93.7% were from the first week after symptom onset. Overall sensitivity and specificity were 93.9% (CI95% 86.5–97.4) and 100% (CI95% 92.1–100), respectively, with a diagnostic accuracy of 96.1% and Kappa coefficient of 0.9. Sensitivity was significantly higher in samples with high viral loads. CONCLUSIONS: The evaluated RDT showed a high sensitivity and specificity in samples mainly obtained during the first week of symptoms and with high viral loads, despite the use of a non-validated sample material. The assay has the potential to become an important tool for early diagnosis of SARS-CoV-2, particularly in situations with limited access to molecular methods.

Since its first occurrence in December 2019, the rapidly emerging SARS-CoV-2 pandemic is 72 causing tremendous public health challenges worldwide (WHO 2020a). Timely detection and 73 isolation of cases and their contacts are considered crucial to help curtail this unprecedented 74 pandemic (Nguyen et al., 2020) . This strategy relies on robust, rapid, and easy-to-perform 75 diagnostic tools that can be used to test large numbers of samples in a short period of time. To 76 date, the recommended diagnostic method for SARS-CoV-2 infection (known as Covid-19) is 77 real-time reverse-transcription polymerase chain reaction (RT-PCR), which was introduced in 78 January 2020 , and is now applied using WHO or CDC protocols (WHO 79 2020b; CDC 2020b) as well as various commercial assays (FIND 2020). 80

The enormous gap between the large number of patients/contacts and the laboratory capacities to 81 perform RT-PCR in a timely manner is a mayor limitation of current public health containment 82 strategies (WHO 2020c). Therefore, there is a critical demand for alternative assays such as 83 antigen detection tests, which, in contrast to antibody tests, can detect the presence of the virus 84 itself in respiratory samples (WHO 2020c). Tests detecting SARS-CoV-2-specific antigen have 85 recently been developed and many of them are now commercially available (FIND 2020). 86

However, the real-world performance of these assays is uncertain and their validation is therefore 87 of high priority (ECDC 2020). Other options include serological tests, but due to their diagnostic 88 limitations in early infections, these tests are currently not recommended for case detection 89 (WHO 2020c; ECDC 2020). Among possible test formats, rapid diagnostic tests (RDTs) should 90 be prioritized, since they are timely, easy to perform, and can serve as point-of-care testing 91 (POCT) (Patel et al., 2020) . Here we present the evaluation of a novel antigen-based RDT for the 92 detection of SARS-CoV-2 in respiratory specimens from suspected Covid-19 cases.

We conducted a study of the diagnostic accuracy of a rapid SARS-CoV-2 antigen detection test 96 compared to RT-PCR. Samples derived from patients with respiratory symptoms and/or fever (Table 3) The test has a cassette format with an external reader and is approved to be used with 172 oropharyngeal swabs, nasopharyngeal swabs, and sputum. In our experience, the system was 173 also observed in the analyses of our Ct values (Fig. 1) . Interestingly, the decline in viral load 196 seemed more pronounced in female patients (Fig. 2) . Accordingly, antigen tests from upper 197 respiratory swabs should be more sensitive in the initial phase of symptomatic infection. This research did not receive any specific grant from funding agencies in the public, commercial, 246 or not-for-profit sectors. 247 

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