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Summary of Covid-19 tests: Developments, Different Types, And Which One Should You Take?

COVID-19 can be diagnosed by detection of the virus (Viral Test) or the immune response against the viral agent (Antibody test). Be aware that unauthorized fraudulent test kits are being marketed to test for COVID-19. The recommendation is to only use Tests approved by the U.S Food and Drug Administration (FDA). According to the Foundation for Innovative New Diagnosis (FIND), at present, 333 "Viral tests" are developed or in the development stage as a diagnostic tool for COVID-19, but only 31 of them had been commercialized with US FDA approval. Also, 347 "Antibody tests" are developed or are in the development stage, but only 12 of them had been approved by the FDA. In the table below, you can see what each of those 2 tests target for COVID-19 diagnosis.




Diagnostic periods to detect SARS-CoV-2 infection

Depending on the time of infection, and the response from the infected individual, a variable load of the virus, antigen, or antibody will be present when taking the sample. In the figure below, you can see an estimation of the duration of the infection and molecular levels reach.


How to overcome the limitations of the different tests?

Virus testing is the recommended test for the first days of infection in order to have early detection, and to reduce treatment costs and morbidity; but asymptomatic carriers, mild cases, sampling failures, complicated procedures, the sensibility of equipment, and other complications could trigger false negatives, thus the combination of RNA-Virus and Antibodies tests is a more accurate approach for the diagnosis of COVID‐19.

Summary

Timing is vital when selecting the appropriate test. After the viral infection, the body's immune defense takes a certain period of time to initiate production of the specific antibodies for this pathogenic organism. The incubation period is estimated to be 4.8 ± 2.6 days, ranging from 2-11 days. COVID-19 virus gene testing (Viral RNA – RT-PCR assay), is more effective during this time. The first antibodies to appear are the IgM, however, they are relatively short-lived and disappear after a few weeks. The IgG antibodies are the ones that provide long-lasting immunity against the initial virus infection or re-infection and can be detected even after the infection is over.

  • If you take an Antibody test in the early stages of the infection, when the antibodies haven’t been produced yet, the test will be a false negative even if the disease is present.

  • If you take a Viral RNA test at the time that antibodies are produced and there is not enough viral load, or at the end of the infection, it will give a false negative result as well.

References.

- Evaluation of current diagnostic methods for COVID-19” by Saadet Alpdagtas, Elif Ilhan, Ebru Uysal, Mustafa Sengor, Cem Bülent Üstündag and Oguzhan Gunduz, 1 December 2020, AIP Bioengineering. DOI: 10.1063/5.0021554

http://aip.scitation.org/doi/10.1063/5.0021554


- Novel coronavirus disease (COVID-19): a pandemic (epidemiology, pathogenesis and potential therapeutics) - ScienceDirect

https://www.sciencedirect.com/science/article/pii/S2052297520300317?via%3Dihub#bib22


#COVID #Viral #Antibodies #diagnosis

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