Viral RNA
The testing of SARS-CoV-2 is grouped into molecular testing and serology testing. The molecular testing includes nucleic acid amplification test (NAAT) such as real-time RT-PCR [7]. According to WHO interim guidance on laboratory testing of COVID-19 in suspected human [7], the respiratory materials were required to collect to perform NAAT. The unique sequence RNA of the virus including nucleocapsid (N), envelope (E), spike protein (S) and RNA-dependent RNA-polymerase (RdRP) genes are targeted to analyze using real-time reverse-transcription polymerase chain reaction (rRT-PCR) [8]. On 23rd January 2020, the first COVID-19 detection kit using rRT-PCR was published which targeted RdRP, N and E gene of SARS-CoV-2 [8]. Up to present, there are many in-house or commercial COVID-19 molecular assays available from worldwide, for instance, 1. ’CDC 2019-nCoV real-time reverse transcriptase PCR diagnostic panel’ was developed by United State Centers for Disease Control and Prevention (US CDC). This diagnostic panel is working with Applied Biosystems 7500 Fast DX Real-Time PCR Instrument with SDS 1.4 software; 2. ‘New coronavirus nucleic acid assay’ which targeted on ORF1ab and N gene was developed by Chinese National Institute for Viral Disease Control and Prevention; 3. Molecular test kits from four companies such as Seegene Inc., Kogene Biotech Co. Ltd., Sd Biosensor Inc., and Solgent Co. were approved by Ministry Food and Drug Safety (MFDS) and Korea Centers for Disease Control and Prevention (KCDCP) which are now widely being used in South Korea [9]. Primer and probe design are critical for the detection of or viral RNA that is easy to mutate. Taiwan Centers for Disease Control provides real-time RT-PCR primers targeting E, RdRp and N gene for first-line screening, confirmatory and additional confirmatory assay, respectively.
The outbreaks of the COVID-19 pandemic have led to the increasing of thousands of active cases every day all over the world, so worldwide are racing against time to find a test to quickly detect the virus and isolate the infected patient from healthy population to stop virus transmission from the further outbreak. The United States Food and Drug Administration (US FDA) is moving fast to approve a few COVID-19 molecular test kits under Emergency Use Authorization (EUA) powers. Cepheid Inc, Mesa Biotech Inc and BioFire Defense LLC were recently granted FDA approval of their rapid diagnostic test that could give the test result reduced to an hour compared to traditional RT-PCR methods that required 3 to 4 hours. On March 27, 2020, Abbott announced the launch of a molecular point-of-care test, which uses an isothermal RNA amplification method to deliver positive results in five minutes and negative results in 13 minutes. It is expected to produce about 5 million tests per month (https://www.abbott.com/corpnewsroom/product-and-innovation/detect-covid-19-in-as-little-as-5-minutes.html).