Considerations in Real-time Reverse Transcription Polymerase Chain Reaction (rRT-PCR) for the Detection of SARS-CoV-2 from Nasopharyngeal Swabs

Abstract

Coronavirus Disease 2019 (COVID-19) was first reported in December 2019, in the City of Wuhan, China. Within the span of a few weeks, the disease had spread to other regions of China and eventually to different parts of the world. COVID 19 has affected 221 countries and territories around the world, with a total of 121,290,697 positive cases and 2,682,554 deaths as on March 17, 2021. Accurate disease diagnosis (for the SARS-Cov-2 virus and variants), coupled to patient isolation are currently critical strategies in restricting disease spread. Due to lack of time during this pandemic the diagnostics assays were not adequately validated. Infected individuals at times could potentially be missed by real-time reverse transcription polymerase chain reaction (rRT-PCR) for SARS-CoV-2 tests due to incorrect/inefficient sampling procedure, low limit of detection and epidemiology of the virus. rRT-PCR test results should be interpreted in conjunction with clinical examination and Computed Tomography (CT), particularly in suspected symptomatic individuals or those with epidemiological history of contact with known COVID-19 cases. Considering the above-mentioned constraints, the current scenario demands rapid and point-of-care tests for detection of SARS-CoV-2 in remote locations. To date, there is no reliable commercially available antigen detection kit. The infected subjects reveal low levels of antibodies against SARS-CoV-2 through the early period of infection. In addition, techniques such as, Digital RT-PCR technology and isothermal RNA amplification with electrochemical biosensors are some of the new technologies currently being developed to provide sensitive and specific SARS-Cov-2 antigen detection. The newly reported variant, SARS-CoV-2 VUI 202012/01 may not influence diagnostic outcomes as worldwide most PCR assays use two or more (including RdRp/ E/ N) reliable gene targets, besides S gene.