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How to Read Rapid COVID Test Results

by Julio Santos January 21, 2022

COVID is an infectious condition caused by the SARS-CoV-2 virus that has had the world on its toes since 2020. While there is still no cure, vaccination and safety guidelines have been a mainstay in prevention and control.

Prompt detection of infection, early isolation, and treatment effectively limit the spread of the virus and reduce the risks of complications and deaths. There are different testing methods, with each having its own mechanism of action and procedure. This article breaks down the process of reading the results of a rapid antigen COVID test.

How does a rapid antigen test work?

A rapid antigen test has areas marked “C”, “T”, and “S”. On one end, there is an elliptical or circular pit marked “S” at the side. This is where the test sample, like saliva or a nasal swab sample, goes into. Away from this section, there is a bigger rectangular pit with areas marked “C” and “T”. This has the test’s cassette for COVID-19 antigens.

The cassette contains SARS-CoV2 antibodies at the area marked “T”. So if the sample has the COVID-19 antigens, they then bind to these antibodies, and a coloured line forms at the T section. If there are no detectable COVID-19 antigens in that sample, then there will be no coloured line at the T area.

How to interpret the results of a rapid COVID test

antigen test card


The area marked “C” displays the control line, which affirms the validity of the test. It must be present for a test to be considered valid.

The area marked “T” displays the test line, which determines whether the result is positive or negative.

If there are two lines–one at C and the other at the area marked “T”, then the result is positive. Sometimes, the line that displays at the T could be faint. It is still considered a positive result, but the test can be repeated.

If there is just one line at the part marked “C”, and no line shows in the area marked “T”, then the result is negative. 

If the test displays a line only at the T area, or no line appears at both the T and C areas, the test is considered void and should be repeated. Invalid results are often due to insufficient diluent volume or incorrect implementation of the procedure. Review the steps and redo with a new test.

In summary:

  • Positive: Coloured lines appear at both the control (C) and test (T) areas.
  • Negative: A coloured line appears at the control (C) area, and no line shows at the test (T) area.
  • Invalid: Either one of the following: 
    • A line appears at the test (T) area, and no line appears at the control (C) area.
    • No line appears at both the control (C) and test (T) areas.

How to get an accurate result

While it is true that there is the possibility of false-negatives with rapid antigen tests, faulty techniques could also lead to getting the wrong result. Follow these tips to avoid getting a false-negative or false-positive result: 

  • Adhere strictly to the manufacturer’s instructions on the pack.
  • Check the expiry date before use. Do not use expired kits.
  • Blow your nose before a nasal swab.
  • Don’t eat or drink anything for at least 10 minutes before taking a saliva sample.
  • Prevent contaminations by being careful. Wash and dry your hands, or use a sanitizer. Avoid touching the part of the swab used to take the sample.
  • Patiently wait until the stipulated time to read the result before disposing of the test.

In conclusion, knowing how to read a rapid test result is as important as taking the test. Everyone has a role to play in limiting the spread of the infection as the world continues to fight this deadly pandemic. It is also vital to follow the COVID-19 protocols laid down by health authorities.

Whenever you need to take a test, get an approved and reliable rapid diagnostic test kit. Early detection via prompt testing helps to minimize the spread of infection, and the person can begin isolation at once if need be.

MyZone rapid antigen tests are reliable and have been authorized by Health Canada. The tests are able to show you results in only 15 to 20 minutes. Quality-assured, Boson Biotech affirms that the test also effectively detects the Omicron variant. 

Order a MyZone test kit online today and keep extra safe!

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