What are the Limitations of Rapid Coronavirus Testing?

There’s a lot being discussed about coronavirus testing these days. Be it on the news, social media, and any other source of information, coronavirus is one topic that is being discussed everywhere. Since the emergence of the novel coronavirus pandemic in 2019, several agencies have worked round the clock to come up with testing techniques that can help detect the presence of the virus. Today there are millions of people all over the world who are being tested for this new coronavirus every day. We are perpetually hearing about these numbers on the media, about how so many thousands of people got tested for the virus in a record number of testing. One of the most commonly used coronavirus testing techniques is the rapid coronavirus test today. But how reliable are these tests? What are the limitations of rapid coronavirus testing? Let’s take a look.

Types of Coronavirus Testing

COVID-19 is an infectious disease that has turned into massive pandemic affecting hundreds of countries and millions of people around the world.(1,2) Caused by the novel coronavirus, this infectious disease affects different people in different ways. Most infected people will go on to develop mild to moderate illness and symptoms, while others will need to be hospitalized and will need to be on ventilator support to help with breathing problems.(3) Many people continue to remain asymptomatic carriers of the disease.(4) Many global organizations, including the US Food and Drug Administration, have been working round the clock these past months to come up with tests for the coronavirus to enable quicker diagnosis and more efficient treatment.(5)

There are three types of tests used to determine whether a person is infected by the novel coronavirus or not. These include:

  • Antibody Tests: These are blood tests that look for symptoms that a person has been infected with the novel coronavirus and has had an immune response. These tests are not used for diagnosing an active coronavirus infection.
  • Antigen Tests: These tests look for specific proteins that are present on the surface of the virus.
  • Genetic Tests: These look for the novel coronavirus’ RNA present in the body through a throat or nose swab or in the saliva samples. The most common type of genetic test used is the polymerase chain reaction test or the PCR test.(6,7)

According to the US Centers for Disease Control and Prevention (CDC), the polymerase chain reaction test is considered to be the ‘gold standard’ of testing for diagnosing SARS-CoV2. SARS-CoV2 stands for severe acute respiratory syndrome coronavirus 2, which is the strain of the coronavirus that is the cause of the ongoing novel coronavirus pandemic. The polymerase chain reaction test is being run by laboratories at hospitals, public health agencies, and even universities.

While some laboratories are able to process samples within one day itself, some take longer, with people having to wait for a week or more to find out if they are positive for COVID-19 or not.(8)

Due to the time taken in getting the results of the polymerase chain reaction test, many laboratories prefer using the antigen test, which is also referred to as the rapid coronavirus est. This test can be done quickly, and the results also become available in as little as just 15 minutes. The test is performed using a nasal or saliva swab. Similar to the polymerase chain reaction test, the antigen tests also show whether a person has an active coronavirus infection.

Even though these antigen tests give faster results allowing more number of tests to be run, there is a high rate of the tests giving false-negative. In fact, as many as half of the negative test results have been found to be inaccurate.(9)

Reliability of Rapid Coronavirus Testing

Even though antigen tests give the results faster, and this allows for more testing to be done, they are known to have a high rate of giving false- negatives. The Vermont Department of Health in the US counts a positive antigen test as a definitely positive only when the results are also confirmed with a polymerase chain reaction test. Other states in the US are also following similar procedures to cut down the rate of false-negatives.(10)

However, at the same time, polymerase chain reaction tests are also not always accurate. Certain studies have found that nearly 29 percent of these tests can also give false negatives.(11)

The accuracy of these coronavirus tests, both antigen and polymerase chain reactions, vary widely depending on the manufacturer and the test itself.

There are many other factors as well that may have an effect on the test results, including how a saliva sample or nasal swab was collected, how the collected sample was transported, how the technician who conducted the test ran the test and if they were trained properly and the equipment that was used to perform the test.(12)

How to Increase Reliability of Testing For Coronavirus?

The primary goal of testing is, of course, to identify people who are actively infected with SARS-CoV-2, and they can be quarantined or isolated so that it doesn’t spread to others. However, suppose people do not receive their test results for two weeks or even longer. In that case, it will no longer matter how accurate the test result is as they have already missed the opportunity to quarantine themselves, and would have already spread the infection to others.

Laboratories can decrease the test backlogs by adding more technicians and equipment or by automating procedures. Some medical experts have also suggested the concept of pooled testing, which is a procedure in which samples are mixed together before testing.(13) If a batch of the samples tests positive, then smaller groups of samples or individual samples are tested, reducing the numbers of tests that the laboratory needs to run.

Another way of increasing reliable testing is to take the testing out of the laboratories and make it possible for a simple and fast test to be run at restaurants, schools, stadiums, airports, and other such places to help identify people who may be infected before they enter these public places. This would significantly lower the risk of transmission, especially in public settings.

For example, at the moment the biotechnology company Sorrento is working on marketing a rapid coronavirus test that has been developed by the Columbia University Fertility Center in New York City by Dr. Zev Williams and his research team.(14) This test is capable of detecting the presence of the novel coronavirus’ RNA in a saliva sample in less than 30 minutes. If the test is positive, the color of the fluid present in the test tube will change to yellow.

While preliminary analysis indicates that this test is highly accurate, similar to the polymerase chain reaction test, but unlike the polymerase chain reaction tests which need specialized equipment to be performed, Sorrento’s saliva test simply requires a heating block, and it can be installed easily in various public places.

Conclusion: Less Accurate Tests Can Also Help

Medical experts agree on the need for decentralized testing. Still, there is no doubt that testing everyone almost every day also means running tens of millions of tests every day, for which we need these tests to be cheap, simple, and available widely.(15)

Since the US Food and Drug Administration compares any newly made coronavirus test to the current polymerase chain reaction test, companies developing the newer tests have to focus on the accuracy of the test at the cost of convenience and speed both. For example, E25 has created a paper strip test that is capable of detecting SARS-CoV-2 infection in just 15 minutes with the use of a saliva sample. However, as of September 2020, it is yet to be approved by the Food and Drug Administration.(16)

While the race is on to develop more accurate tests, in the present situation for every testing, less accurate testing with antigen and PCR tests are still doing to work. This is because even though the rapid coronavirus test is not perfect, it is always better than not having any test at all or stopping the testing process itself altogether.

References:

  1. COVID, T.C. and Team, R., 2020. Severe Outcomes Among Patients with Coronavirus Disease 2019 (COVID-19)-United States, February 12-March 16, 2020. MMWR Morb Mortal Wkly Rep, 69(12), pp.343-346.
  2. Mehta, P., McAuley, D.F., Brown, M., Sanchez, E., Tattersall, R.S., Manson, J.J. and HLH Across Speciality Collaboration, 2020. COVID-19: consider cytokine storm syndromes and immunosuppression. Lancet (London, England), 395(10229), p.1033.
  3. Fauci, A.S., Lane, H.C. and Redfield, R.R., 2020. Covid-19—navigating the uncharted.
  4. Bai, Y., Yao, L., Wei, T., Tian, F., Jin, D.Y., Chen, L. and Wang, M., 2020. Presumed asymptomatic carrier transmission of COVID-19. Jama, 323(14), pp.1406-1407.
  5. U.S. Food and Drug Administration. 2020. Coronavirus Testing Basics. [online] Available at: <https://www.fda.gov/consumers/consumer-updates/coronavirus-testing-basics> [Accessed 19 September 2020].
  6. Beltrán‐Corbellini, Á., Chico‐García, J.L., Martínez‐Poles, J., Rodríguez‐Jorge, F., Natera‐Villalba, E., Gómez‐Corral, J., Gómez‐López, A., Monreal, E., Parra‐Díaz, P., Cortés‐Cuevas, J.L. and Galán, J.C., 2020. Acute‐onset smell and taste disorders in the context of COVID‐19: a pilot multicentre polymerase chain reaction based case–control study. European journal of neurology.
  7. Chen, Z., Li, Y., Wu, B., Hou, Y., Bao, J. and Deng, X., 2020. A patient with COVID-19 presenting a false-negative reverse transcriptase polymerase chain reaction result. Korean Journal of Radiology, 21(5), p.623.
  8. Azcentral.com. 2020. [online] Available at: <https://www.azcentral.com/story/news/local/arizona-health/2020/07/30/covid-19-test-backlog-persists-states-largest-processor-sonora-quest/5549328002/> [Accessed 19 September 2020].
  9. Science | AAAS. 2020. Coronavirus Antigen Tests: Quick And Cheap, But Too Often Wrong?. [online] Available at: <https://www.sciencemag.org/news/2020/05/coronavirus-antigen-tests-quick-and-cheap-too-often-wrong#> [Accessed 19 September 2020].
  10. Vermont Department of Health. 2020. Coronavirus (COVID-19). [online] Available at: <https://www.healthvermont.gov/response/coronavirus-covid-19> [Accessed 19 September 2020].
  11. Woloshin, S., Patel, N. and Kesselheim, A.S., 2020. False Negative Tests for SARS-CoV-2 Infection—Challenges and Implications. New England Journal of Medicine.
  12. Mughal, Z., Luff, E., Okonkwo, O. and Hall, C.E.J., 2020. Test, test, test–a complication of testing for coronavirus disease 2019 with nasal swabs. The Journal of Laryngology & Otology, pp.1-4.
  13. Centers for Disease Control and Prevention. 2020. Information For Laboratories About Coronavirus (COVID-19). [online] Available at: <https://www.cdc.gov/coronavirus/2019-ncov/lab/pooling-procedures.html> [Accessed 19 September 2020].
  14. Sorrento Therapeutics. 2020. Sorrento Announces License From Columbia University For Rapid On-Site Detection Test For SARS-Cov-2 Virus In Saliva | Sorrento Therapeutics. [online] Available at: <https://investors.sorrentotherapeutics.com/news-releases/news-release-details/sorrento-announces-license-columbia-university-rapid-site> [Accessed 19 September 2020].
  15. Madrigal, R., 2020. The Plan That Could Give Us Our Lives Back. [online] The Atlantic. Available at: <https://www.theatlantic.com/health/archive/2020/08/how-to-test-every-american-for-covid-19-every-day/615217/> [Accessed 19 September 2020].
  16. NDTV Gadgets 360. 2020. Biotech Develops E25bio 15-Minute Test For COVID-19. [online] Available at: <https://gadgets.ndtv.com/science/news/tata-backed-mit-startup-develops-15-minute-test-for-covid-19-2215690> [Accessed 19 September 2020].

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