Analytical Evaluation of Visby Medical RT-PCR Portable Device for Rapid Detection of SARS-CoV-2

Abstract

Extended community testing constitutes one of the main strategic pillars in controlling the COVID-19 pandemic. Reverse transcription PCR (RT-PCR) targeting the SARS-CoV-2 genome on nasopharyngeal swab samples is currently the reference test. While displaying excellent analytical sensitivity and specificity, this test is costly, often requires a substantial turnaround time, and, more importantly, is subject to reagent and other material shortages. To complement this technology, rapid antigen tests have been developed and made available worldwide, allowing cheap, quick, and decentralized SARS-CoV-2 testing. The main drawback of these tests is the reduced sensitivity when RT-PCR is the gold standard. In this study, we evaluate Visby an innovative, portable, easy-to-use RT-PCR point-of-care (POC) diagnostic device. Our retrospective analysis shows that overall, compared to the Cobas 6800 RT-qPCR assay (Roche), this RT-PCR POC technology detects SARS-CoV-2 RNA with 95% sensitivity (95%CI = 86.3-99%) and 100% specificity (95% CI = 80.5-100%). For samples with cycle-threshold values below 31, we observed 100% sensitivity (95% CI = 66.4-100%). While showing an analytical sensitivity slightly below that of a standard RT-qPCR system, the evaluated Visby RT-PCR POC device may prove to be an interesting diagnostic alternative in the COVID-19 pandemic, potentially combining the practical advantages of rapid antigen tests and the robust analytical performances of nucleic acid detection systems.

Keywords: POCT techniques; SARS-CoV-2; rapid diagnostic techniques.

Figure 1

(A) Schematic steps for Visby Medical kit procedure. (1) Kit contents. (2) Patient sample preparation, with dilution buffer and cassette. (3–5) The sample is put into the dilution buffer and mixed by inversion. (6–7) 650 uL of the diluted sample is inserted into the device using the pastette. (8) Buttons 1, 2, and 3 are pushed, and the device is connected to electrical power. (9) Results displayed. A white checkmark appears, indicating that the test is in progress (see description below). (B) The left panel shows the white or green or red check marks denoting correct power and processing of the device, a valid test result ready to be read, or an invalid result due to an electrical error, respectively. The right panel shows an example of a valid (green light) and positive (visible upper and lower purple spots) or negative (only the upper purple spot is visible).

Figure 2

Detection of SARS-CoV-2 by Visby device based on viral loads and the time of symptom onset. SARS-CoV-2 viral loads by the time of symptom onset for the symptomatic and RT-qPCR positive individuals. Black and red dots represent positive or negative Visby results, respectively. Dotted line: 6 log₁₀ SARS-CoV-2 RNA copies/mL shows the VL threshold limit determining the number of culturable viruses. Note: Samples classified at day 0 include 4 samples with unknown dates of symptoms.