COVID-19 testing

CDC 2019-nCoV Laboratory Test Kit.jpg


COVID-19 testing involves analyzing samples to assess the current or past presence of SARS-CoV-2. The two main branches detect either the presence of the virus or of antibodies produced in response to infection. Tests for viral presence are used to diagnose individual cases and to allow public health authorities to trace and contain outbreaks. Antibody tests instead show whether someone once had the disease. They are less useful for diagnosing current infections because antibodies may not develop for weeks after infection. It is used to assess disease prevalence, which aids the estimation of the infection fatality rate.

Individual jurisdictions have adopted varied testing protocols, including whom to test, how often to test, analysis protocols, sample collection and the uses of test results. This variation has likely significantly impacted reported statistics, including case and test numbers, case fatality rates and case demographics. Because SARS-CoV-2 transmission occurs days after exposure (and before onset of symptoms) there is an urgent need for frequent surveillance and rapid availability of results.

Test analysis is often performed in automated, high-throughput, medical laboratories by medical laboratory scientists. Alternatively, point-of-care testing can be done in physician's offices and parking lots, workplaces, institutional settings or transit hubs.

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Testing protocols

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Testing statistics by country

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Methods

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Positive viral tests indicate a current infection, while positive antibody tests indicate a prior infection. Other techniques include a CT scan, checking for elevated body temperature, checking for low blood oxygen level, and the deployment of detection dogs at airports. Detection of the virus Reverse transcription polymerase chain reaction Polymerase chain reaction (PCR) is a process that amplifies (replicates) a small, well-defined segment of DNA many hundreds of thousands of times, creating enough of it for analysis. Test samples are treated with certain chemicals that allow DNA to be extracted. Reverse transcription converts RNA into DNA. Reverse transcription polymerase chain reaction (RT-PCR) first uses reverse transcription to obtain DNA, followed by PCR to amplify that DNA, creating enough to be analyzed. RT-PCR can thereby detect SARS-CoV-2, which contains only RNA. The RT-PCR process generally requires a few hours. Real-time PCR (qPCR) provides advantages including automatio
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