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Rapid Antigen Test Vs RT-PCR Test – What to Take and When

December 17, 2021
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There are two types of COVID-19 tests – RT-PCR test and rapid antigen test (Representational)

With Christmas just around the corner The number of COVID-19 cases is increasingIt’s important to keep getting tested when you have symptoms, have been exposed to the virus, or are traveling to a high-risk environment.

We now have access to PCR tests (known as RT-PCR, or reverse transcription-polymerase chain reaction, tests) And Rapid antigen test to detect SARS-CoV-2, the virus that causes COVID.

So which test should you use? And what’s the difference?

how tests work

In Australia, PCR tests are used to diagnose SARS-CoV-2 infection. This test looks for SARS-CoV-2 genetic material.

RT-PCR converts viral RNA into DNA and amplifies the genetic sequence, creating billions of copies where these copies can be detected.

Because the test can amplify small amounts of viral genetic material, it is considered the gold standard and can detect infection at earlier stages than other tests such as rapid antigen tests.

Here’s how the PCR test works.

Instead the rapid antigen test detects viral protein, The proteins bind to the antibody solution which becomes fluorescent to indicate the presence of the protein.

Rapid antigen tests are:

  • Faster than PCR tests (15-20 minutes vs hours to days to get results)

  • This can be done at home, compared to waiting in line and waiting for a swab, which then has to be analyzed in a lab.

But they are less sensitive than PCR tests because there is no amplification process.

Here’s how to do a rapid antigen test at home.

How effective are they?

While both tests are more likely to correctly detect infection when a person’s viral load is high, PCR tests are more sensitive than rapid antigen tests.

One Australian Studies Comparing the sensitivity (correctly diagnosing SARS-CoV-2 infection) of one type of rapid antigen test compared to the PCR test, found 77% of the positive antigen test results aligned with the PCR test results.

This increased to 100% when people were tested within a week of the onset of symptoms.

medical goods administration Provides a list of approved rapid antigen tests whose results align with PCR testing 80–95% of the time, provided the test is performed within a week of symptom onset. Some of these tests are rated as having very high sensitivity with 95% agreement with PCR tests.

When to take which test?

Take RT-PCR Test if you:

  • have COVID symptoms

  • Known to have come into contact with someone with COVID

  • Do a rapid antigen test and get a positive result, as PCR confirmation is needed

  • need to be released from quarantine or isolation by your health department

  • are required by the health department to obtain permission to travel to a place.

A PCR is the test of choice in these situations because it is more accurate in diagnosing infection.

consider one rapid antigen test if you:

  • planning to visit a vulnerable site (for example, an aged care facility)

  • are planning to have contact with someone at high risk of COVID (for example, an elderly person or someone on immunosuppressive treatment), and you want to protect them

  • Have COVID symptoms but can’t go to PCR test site

  • going to an event where a lot of people will be meeting, especially if it is being held indoors risk of transmission is much more

  • Want to quickly test whether you may have SARS-CoV-2 infection

  • Are part of a regular COVID surveillance program (some workplaces require this, especially in situations where the person is not fully vaccinated).

Rapid antigen test is considered as a screening tool. In other words, it may indicate that you may be infected, but a PCR test is needed to confirm the result.

While a negative rapid antigen test result is not a guarantee that you are not infected, it does offer more protection than not testing your contacts.

How Often Should I Take a Rapid Antigen Test?

It depends on the reason for which you are taking the exam. If you are part of a monitoring program, take the test when you are asked.

If you don’t have symptoms, get tested two to three times Testing over a week may help improve sensitivity as the viral load waxes and wanes. Test sensitivity will be highest when the viral load is at its peak.

How does Omicron affect version testing?

What appears to be a highly mutated Omicron variant still being explored Both by PCR and Rapid Antigen Test.

Usually, a PCR test indicates whether you have a SARS-CoV-2 infection, but not which type you have. genome sequencing Need to find out.

However, some PCR tests look for a specific genetic sequence that is missing in the omicron variant (S gene target failure is called) Those special PCR tests can not only detect a positive result, but also find out whether it is likely to be an omicron variant. Conversation

(Author: thia van de mortel, Professor, Nursing and Deputy Head (Learning and Teaching), School of Nursing and Midwifery, Griffith University,

This article is republished from Conversation Under Creative Commons license. read the original article,

(Except for the title, this story has not been edited by NDTV staff and is published from a syndicated feed.)

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