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Home > Blog > What Is the Difference Between RT PCR and Rapid Antigen Test?

What Is the Difference Between RT PCR and Rapid Antigen Test?

What Is the Difference Between RT PCR and Rapid Antigen Test?

Max Lab

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.

What Does RT PCR Stand For?

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.

What Happens in an RT PCR Test?

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.

What is the Meaning of CT in RT PCR Tests?

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.

What is an Antigen Test?

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.

What is a Rapid Antigen Test?

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.

The Differences between the RT PCR and Rapid Antigen Tests

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.

  • The Time Taken: It takes much longer to get the results of an RT PCR test, while the rapid test’s results take hardly 10-15 minutes.
  • Who is Involved in Conducting the Test: For the RT PCR test, the samples are sent to a diagnostics laboratory, where they are tested by skilled technicians. The RAT on the other hand can be performed by anyone. In fact, rapid test kits are also available in the market that people can purchase and do the test by themselves at home.
  • Where is the Test Conducted: The RT PCR test sample collection can be done from one’s home or at a collection centre, but the testing can only be performed in a lab. The rapid antigen test however is a point-of-care test, which means that it can be conducted anywhere, at a lab, clinic, or at home.
  • Costs: The rapid antigen test is much more cost-effective as compared to the RT-PCR test.
  • Accuracy: The RT PCR test is a highly accurate test that is very likely to return a positive result if an individual has been infected with the virus. However, there is also a very slight chance that the test may detect residual virus in a person’s body even after they have recovered and return a false positive report. The rapid test is not as sensitive as the RT PCR test and tends to be more accurate in the initial days of infection when the largest amounts of the virus are present in the body. Though it provides quick results, it is always recommended to follow the same with an RT PCR test for confirmation.

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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