Jul 07, 2020
As documented by media outlets, it’s known by most people how on-site testing works, you drive to the testing site, a person in white PPE comes up and sticks a cotton swab into to your nose, twists it a bit and then that’s it. Or perhaps it was a finger prick to get results from your blood. But what happens to your swab in the lab? How does a possible infected person’s blood result in either a positive or negative result? What are the downsides to certain tests? Those are the questions that are being asked by quite a few people who are curious as to what goes on behind the scenes.
Molecular Testing: It’s in your DNA
For molecular testing, a patient with the virus will also have its genetic makeup in their body as well, which can be detected in the upper and lower respiratory tracts in patients. Molecular testing already has been routinely used with other acute respiratory viral infections through a lab procedure called reverse transcription polymerase chain reaction, abbreviated as RT-PCR1.
What is PCR? How Accurate are Results?
PCR requires DNA in order for the procedure to work, so an enzyme called Reverse Transcriptase will take the RNA found in coronavirus to create the DNA from the patient sample. This sample will then be amplified, copied multiple times during several heating and cooling cycles and then compared to the virus of interest via gel electrophoresis (in this case the SARS-CoV-2 virus) in order to garner results. The infamous testing site nose swab goes in this category of testing as well as an at home kit called Pixel by LabCorp2, as an example. Results often arrive within hours or a few days and are quite accurate, however, the chance of false negatives are possible.
Serological Testing: Using Your Body’s Natural Defense System
Serological testing involves pricking the finger for blood to test for detecting antibodies, this type of testing does not require an extra equipment, so it can be used at the place of care or directly in a lab. Serological tests have a much faster rate for when results will come back, the average being about 1-2 days. So how does it work? When someone has been infected by the virus, their body will produce antibodies, a protein that helps your immune system mount a response, there are several types of antibodies as well. In this case, the presence of the antibody immunoglobin M(IgM) indicates a more recent contact with the virus, if the blood sample has concentrations of another type of antibody, called immunoglobin G or IgG, it indicates the infection is at a later stage in the body.
What is ELISA? How Accurate are Results?
The technique to detect antibodies in blood is called ELISA or enzyme linked immunological assay, where the sample will undergo several incubations and washing steps, linking antibodies to an enzyme. When this setup is exposed to a substrate, there will be a color change, indicating a positive result. In term of accuracy, since it does take time-about several days to even weeks-for the human body to produce antibodies in response to any pathogen, it’s not the best indicator of a current infection, thus creating possible false negatives so it’s more useful in finding individuals who were infected and then recovered from the virus.
Are there other types of diagnostic tests? What’s next?
Molecular and Serological testing are the two main mainstream forms of diagnostic testing currently on the market worldwide. Currently several developers, such as Cold Spring Harbor Laboratory4 and Casper Biotech5, are using CRISPR technology to develop diagnostic tools to assist in rapid testing, CRISPR involves editing the genome which can be used to reverse errors found in our genetic code to prevent anything from disease to improving crops. Another method currently being researched is the use of Spectrophotometry by Copenhagen Nanosystems ApS which involves the use of saliva and the use of a device called a spectrophotometer to measure the reflective and transmission properties of the saliva via light to detect the whether the patient is infected, not infected and even possible immunity to the virus6. This research will not only assist with more rapid and accurate diagnoses of COVID-19 but possibly assist in future diagnoses of other viral infections.
Want to learn more? Here are the sources used in this article!
1. Billingsley, A., PharmD, RPh. (2020, May 22). The Latest on Coronavirus Testing: New Methods, Accuracy, and Availability- GoodRx. Retrieved June 25, 2020, from https://www.goodrx.com/blog/coronavirus-covid-19-testing-updates-methods-cost-availability/
2. Corp, L. (2020, June 02). COVID-19. Retrieved June 25, 2020, from https://www.pixel.labcorp.com/covid-19
3. Biolabs, C. (2020). The Novel Coronavirus (SARS-CoV-2) Nucleoprotein (NP) ELISA Kit. Retrieved June 25, 2020, from https://www.creativebiolabs.net/the-novel-coronavirus-sars-cov-2-nucleoprotein-np-elisa-kit_81.htm
4. Abbott, T., Dhamdhere, G., Liu, Y., Lin, X., Goudy, L., Zeng, L., . . . Qi, L. (2020, January 01). Development of CRISPR as a prophylactic strategy to combat novel coronavirus and influenza. Retrieved June 25, 2020, from https://www.biorxiv.org/content/10.1101/2020.03.13.991307v1
5. Lucia, C., Federico, P., & Alejandra, G. (2020, January 01). An ultrasensitive, rapid, and portable coronavirus SARS-CoV-2 sequence detection method based on CRISPR-Cas12. Retrieved June 25, 2020, from https://www.biorxiv.org/content/10.1101/2020.02.29.971127v1
6. Højlund-Nielsen, E. (2020, April 06). NanoCuvette™ SARS-CoV-2. Retrieved June 25, 2020, from https://cphnano.com/nanocuvette-sars-cov-2/
Image Credits(in order)
Costa, J. R. (2020). [PCR Step By Step Graphic]. Retrieved June 25, 2020, from https://mindthegraph.com/profile/julianarcosta/what-is-pcr#/
University, E. (2020). [Digital image]. Retrieved June 25, 2020, from https://news.emory.edu/stories/2020/05/coronavirus_antibody_study_sheds_light_on_immunity/thumbs/COVID%20Serology%20infographic.jpg
Diagnostics, E., Inc. (2020). [ELISA Assay Protocols for COVID-19]. Retrieved June 25, 2020, from https://images.squarespace-cdn.com/content/v1/52545951e4b021818110f9cf/1586209852455-ZR4HVO9TODTIUBS0R25S/ke17ZwdGBToddI8pDm48kBWxvBewuLY8tzxivUuchzIUqsxRUqqbr1mOJYKfIPR7LoDQ9mXPOjoJoqy81S2I8N_N4V1vUb5AoIIIbLZhVYxCRW4BPu10St3TBAUQYVKcL_oPDtlx0Wk2Jur56KWiY_bCys8NprZ_oY1oSKb259KDqAMi3SmW-gJLK4fJj8yt/COVID-layout.PNG?format=2500w