Standard Diagnostic Methods

Topic Overview:

Within this page, two standard diagnostic methods are introduced and explained. Below are figures which portray the steps of real-time RT-PCR and one example of an antibody test for the detection of SARS-CoV-2. Moreover, there is a table comparing the two diagnostic methods, in addition to keywords that relate to this topic and relevate papers for additional research. Disclaimer: we are evaluating real time RT-PCR but shorten it to RT-PCR throughout the website for brevity (real time PCR refers to the fact that we are tracking the increase in the fluorescent signal from amplification in real time).

Reverse Transcription Polymerase Chain Reaction (RT-PCR)

Reverse Transcription Polymerase Chain Reaction (RT-PCR) is the current gold standard diagnostic method for the COVID-19 virus. RT-PCR is a diagnostic method that amplifies and measures the quantity of a specific genetic sequence that is targeted (in this case it is the SARS-CoV-2 virus). A sample for this diagnostic is usually taken using either a nasopharyngeal swab or an oropharyngeal swab, which is then immediately placed in a tube containing a viral transport medium (a substance that controls contamination). This sample is then transported to a lab to undergo one-step RT-PCR (more details are shown in the figure below). Additional information on RT-PCR can be found in the RT-PCR Diagnostics Methods page.

Figure 1: This figure shows the process of Reverse Transcription Polymerase Chain Reaction (RT-PCR) to replicate and amplify the RNA genetic sequence from SARS-CoV-2 to determine if the COVID-19 virus is present. Before the process of RT-PCR, the extraction of the RNA strand from the patients sample must be isolated. The figure then shows the RNA being reverse transcirbed to cDNA and amplified by qPCR. Additionally, the results and primers/probes on the genome are visualized through graphs provided. (Reprinted from "COVID-19 Diagnostic Test through RT-PCR", by BioRender, April 2020, retrieved from https://app.biorender.com/biorender-templates/figures/5e99f5395fd61e0028682c01/t-5e8f21be13f46000ab9f6806-covid-19-diagnostic-test-through-rt-pcr).

COVID-19 Detection with Antibody Diagnostic Test

Antibody based tests (also known as serology tests) use blood samples to determine if an individual has been exposed to the COVID-19 infections in their past and can not determine if you are currently infected with the COVID-19 virus (Mayo Clinic, 2020). The blood samples taken are run on either an ELISA assay or lateral flow assay (the figure below demonstrates the lateral flow assay) which detects the presence of SARS-CoV-2 antibodies (proteins that fight off infections) within the plasma of the blood. Ultimately, if an individual shows traces of these antibodies, it indicates that they have been infected with the virus, whether they experienced symptoms or not. Provided below is an image that shows the steps of the Serologic Diagnostic Test.

Figure 2: This figure shows the steps taken when testing for the presence of antibodies. Provided is a picture of what the lateral flow assay looks like and how to read it. Ultimately, this assay helps us to determine the results of the serologic test. Throughout the steps it is evident that a blood sample is initally taken and mixed with a buffer, where this solution is then incubated.

Comparison of RT-PCR Diagnostic Tests and Antibody Based Tests

RTPCR/antibody

Figure 3: This figure compares various factors that are taken into account between the RT-PCR Diagnostics Tests and the Antibody Based Tests for the detection of the COVID-19 virus. The criteria above only differentiates these tests based off certain elements such as: sample testing, results, what it tests for, time to get results, reason for receiving the test, how it works and how it's assessed. Although there are many components included, this is not all that shows the distinctions of these two tests.

Key words

ELISA Assay

ELISA stands for Enzyme-linked immunosorbent assay, which is a test that detects and measures measures antibodies, antigens, proteins and glycoproteins in biological samples (such as blood).

Polymerase Chain Reaction (PCR)

Polymerase Chain Reaction (PCR) is a technique used to amplify and quantify small segments of DNA. Ultimately, it is a process that works to make billions of copies of a specific part of a DNA segment in order for scientists to study the gene in detail. Disclaimer: PCR is not solely used to study genes, it has many various different applications.

Antibody

A protein that works to fight off any harmful substances such as antigens. Antibodies are disease specific and can provide protection from contracting the specific virus again and therefore building immunity.

Relevant Papers

COVID-19 target: A specific target for novel coronavirus detection

This paper addresses the idea of targeting a more specific gene on the SARS-CoV-2 virus, in order to increase the efficiency of diagnosis. Typically RT-PCR targets either the RdRP, E or N genes, but this paper proposes a different target known as the ORF8 gene. By targeting for a gene that is strictly specific to this strain of the COVID-19 infection, it will decrease the rate of false positive tests and increase the accuracy of detection. Ultimately, this paper connects directly to our topic by exploring different targets which will make the diagnostic tests more specific and accurate.

2. COVID-19 Serology Testing Explained

This article gives various details about the different factors of the antibody test. It describes how this test uses blood samples to detect if there are antibodies present within the plasma of the blood that target for the specific SARS-CoV-2 antigen. Additionally it includes useful information on antigens, by introducing and describing the different viral antigens that have been used to detect these specific antibodies (3). This information is useful towards our research because it provides more information on other diagnostics such as antibody tests and antigen tests which we touch upon on this page and also on the Emerging Diagnostics page.

References

Kakhki, R.K., Kakhki, M.K., Neshani, A., 2020. COVID-19 target: A specific target for novel coronavirus detection [WWW Document]. Gene reports. URL https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7261075/ (accessed 10.20.20).
Iwasaki, S., Fujisawa, S., Nakakubo, S., Kamada, K., Yamashita, Y., Fukumoto, T., Sato, K., Oguri, S., Taki, K., Senjo, H., Sugita, J., Hayasaka, K., Konno, S., Nishida, M., & Teshima, T. (2020). Comparison of SARS-CoV-2 detection in nasopharyngeal swab and saliva. The Journal of infection, 81(2), e145–e147.
Hagen, A., 2020. COVID-19 Serology Testing Explained [WWW Document]. URL https://asm.org/Articles/2020/May/COVID-19-Serology-Testing-Explained (accessed 11.10.20).
Bibel, B., 2020. COVID-19 testing [WWW Document]. The Bumbling Biochemist. URL https://thebumblingbiochemist.com/365-days-of-science/covid-19-testing/ (accessed 11.10.20).
COVID-19 antibody testing [WWW Document], 2020. [WWW Document]. Mayo Clinic. URL https://www.mayoclinic.org/tests-procedures/covid-19-antibody-testing/about/pac-20489696 (accessed 11.10.20).
Coronavirus Disease 2019 Testing Basics [WWW Document], n.d. [WWW Document]. U.S. Food and Drug Administration. URL https://www.fda.gov/consumers/consumer-updates/coronavirus-disease-2019-testing-basics (accessed 11.11.20).
Vuong, K.T., 2020. Coronavirus Blood Test (antibody) vs. Swab Test (PCR) vs. Rapid COVID Test - Which is Best? [WWW Document]. Mira. URL https://www.talktomira.com/post/coronavirus-blood-test-antibody-swab-test-pcr-saliva-test-differences (accessed 11.11.20).
Corman, V.M.et. al, n.d. Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR [WWW Document]. Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin. URL https://pubmed.ncbi.nlm.nih.gov/31992387/ (accessed 12.8.20).

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