Nov 16, 2022
During the COVID-19 pandemic, RT-PCR and rapid antigen tests gained a lot of popularity as they were the most preferred ways of detecting if a person was suffering from COVID-19. However, unlike the vaccines that were developed to help fight the infection, these tests were not new. In fact, they have been around for quite some time and have been used to help detect the presence of a viral infection.
Antigen tests generally look for the presence of surface proteins of a virus, the genetic material, RNA, which instructs the virus to produce these proteins, is what an RT PCR test detects. Both tests involve sample collections where swabs are collected from the back of the throat and the nose, but that is where all similarities between the two tests end.
What the RT PCR test and what the rapid antigen test is detecting and how they are performed affect how long the results take and how accurate the tests are as well.
Reverse transcription polymerase chain reaction is the full form of RT PCR. Before understanding what RT PCR is, it’s necessary to understand the basics of PCR. PCR is a laboratory technique that monitors the amplification of a targeted DNA molecule. As viruses have RNA instead of DNA, the reverse transcription of RNA into DNA is carried out.
RT PCR tests have high specificity and high sensitivity and are the preferred option for detecting viruses as they can detect their presence even when there are very small amounts of pathogens present in the body so that the person is not even displaying any symptoms. During this test, a small amount of genetic material in a sample is amplified with the use of an enzyme called polymerase, which causes the sample to produce copies.
The cycle threshold or CT value in the RT PCR report is what defines the severity of the disease and the viral load. It refers to the number of cycles it takes for the fluorescence of the virus to be detected over the background signals or the number of cycles it takes for the viral load to be detected.
An antigen test is performed to detect the presence of surface antigens, which are certain types of proteins that can be found on the surface of a virus. Antigen tests are different from antibody tests, which look for the presence of antibodies that are produced by the body to fight off a virus. Antigens appear much sooner in the body than antibodies.
The rapid antigen test (RAT) is an immunochromatographic assay that provides results that may be seen by the naked eye. This is a qualitative test that can detect the presence of a virus but cannot measure the viral load.
What is Meant by Positive RT PCR and Positive RAT Test Results: The RT PCR test detects the presence of the virus’s RNA in a sample, while the rapid antigen test looks for the presence of surface antigen.
While the cost-effective rapid antigen test is quite useful in conducting mass screening tests, the accuracy of RT PCR is always necessary for a confirmed diagnosis.
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