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PETALING JAYA: There are two popular known Covid-19 tests available and used by health authorities around the world to detect the virus.
The two tests, the reverse transcription polymerase chain reaction (RT-PCR) and the rapid antigen test kit (RTK-Ag), require pharyngeal or nasal swab specimens.
RT-PCR is considered the gold standard in the diagnosis of the Covid-19 virus.
It can detect whether a person has an active Covid-19 infection and the test typically has high sensitivity rates, although this also means that the sample must be carefully prepared to avoid contamination.
RT-PCR is a molecular test that can detect minute amounts of ribonucleic acid (RNA) from the Covid-19 virus in a nasal or throat swab sample taken from an individual.
Chemicals are used on the swab to remove other substances and extract only the RNA from the sample.
RNA is converted to DNA through the process of “reverse transcription,” and scientists add extra short pieces of DNA to build DNA strands and to add marker tags to detect the virus.
The mixture is placed in a machine that creates copies of the viral DNA, during which the marker labels release a fluorescent dye that is measured by a computer.
Depending on the laboratory and logistics, results can be obtained in two hours or up to several days if the sample has to be shipped different distances.
The RTK-Ag test, on the other hand, is faster than the RT-PCR test, as it can generate results in 15 to 30 minutes.
As such, RTK-Ag has the advantage of detecting Covid-19 outbreaks rapidly and in large numbers, but its accuracy is less than the RT-PCR test and can produce false negative results (leading to a false sense of security. ).
The Ministry of Health uses RTK-Ag as an alternative to RT-PCR in certain situations, in order to obtain test results in less time in circumstances where molecular tests are not available.
Antigen tests work by detecting specific proteins on the surface of the virus, unlike the RT-PCR test that detects the genetic material of the virus.
Yet another test for Covid-19 is the antibody test, which unlike RT-PCR and RTK-Ag tests, is detected through a blood sample. Samples are obtained by pricking the finger or drawing blood, and results can be obtained in a few days.
However, the antibody test is not suitable for detecting active Covid-19 infections, as it can only show that a person has been (or has never been) infected with the virus in the past.
The test detects antibodies, which are proteins made by a person’s immune system after they have been infected or vaccinated.
According to the US Centers for Disease Control and Prevention, it will take a person’s body one to three weeks after infection to produce antibodies.
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