Abstract
COVID-19 diagnostics was quickly ramped up worldwide early 2020 based on the detection of viral RNA. However, based on the scientific knowledge for pre-existing coronaviruses, it was expected that the SARS-CoV-2 RNA will be detected from symptomatic and at significant rates also from asymptomatic individuals due to persistence of non-infectious RNA. To increase the efficacy of diagnostics, surveillance, screening and pandemic control, rapid methods, such as antigen tests, are needed for decentralized testing and to assess infectiousness. A novel automated mariPOC SARS-CoV-2 test was developed for the detection of conserved structural viral nucleocapsid proteins. The test utilizes sophisticated optical laser technology for two-photon excitation and individual detection of immunoassay solid-phase particles. We validated the new method against qRT-PCR. Sensitivity of the test was 100.0% (13/13) directly from nasopharyngeal swab specimens and 84.4% (38/45) from swab specimens in undefined transport mediums. Specificity of the test was 100.0% (201/201). The test's limit of detection was 2.7 TCID50/test. It showed no cross-reactions. Our study shows that the new test can detect infectious individuals already in 20 min with clinical sensitivity close to qRT-PCR. The mariPOC is a versatile platform for syndromic testing and for high capacity infection control screening of infectious individuals.
Highlights
COVID-19 diagnostics was quickly ramped up worldwide early 2020 based on the detection of viral RNA
In the case of COVID-19 diagnostics, the fact that viral RNA persistence can be detected without viable virus for months, has been a known clinical challenge, as diagnostics relied in the beginning of the pandemic solely on nucleic acid amplification tests (NAAT) d etection[18], the efficacy of which is in ruling out positivity
We have previously shown that the presence of coronavirus OC43 N-protein in the nasopharynx correlates with the respiratory tract infection symptoms[32]
Summary
COVID-19 diagnostics was quickly ramped up worldwide early 2020 based on the detection of viral RNA. Our study shows that the new test can detect infectious individuals already in 20 min with clinical sensitivity close to qRT-PCR. The interpretation of gene positivity in clinical specimens has been challenging since the viral RNA is detected at similar rates and qRT-PCR cycle threshold (Ct) values from symptomatic and asymptomatic individuals. The viral RNA is co-detected with genomes of other respiratory viruses[4,5,6,7] This is the case for the SARS-CoV-28,9. Pekosz et al (2020) showed that the detection of N-protein by an antigen test correlates with SARS-CoV-2 viral culture more accurately than qRT-PCR13. Zhang et al (2021) found that parts of the reverse-transcribed SARS-CoV-2 RNA can integrate ex vivo into the human genome without the ability to yield infectious viruses and suggest that this could explain at least partly the long term RNA shedding, in vivo evidence remains to be s een[23]
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