COVID-19 testing: who, when and why?

COVID-19 tests are part of the arsenal available to fight the pandemic. Using them properly can save lives!

COVID-19: a sometimes hidden infection

COVID-19 is not always easy to detect. It is estimated that roughly 15 to 30% of people infected with the coronavirus (SARS-CoV-2) have no symptoms. However, they can still spread the virus. Additionally, the most common symptoms (cough, fever, headache, muscle aches, chills) are similar to those of other illnesses such as the flu or the common cold. Therefore, it is easy to have COVID-19 without knowing it.

Symptoms usually appear 5 to 7 days after having been infected (in some cases, 2 to 12 days). As a result, an individual can be contagious and spread the virus even before showing symptoms. Testing is the only way to confirm COVID-19 infection with certainty. Obtaining a clear diagnosis makes it possible to choose the appropriate treatment measures, to protect the people around them and to avoid spreading the infection on a larger scale.

Therefore, screening tests help to limit the spread of the virus, and also to determine the number of cases in a given population or area. These tests also contribute to a better understanding of the virus and the pandemic, as well as to help choose the most effective public health measures.

 

Screening tests: who and when

Anyone with signs or symptoms indicative of COVID-19 should be tested at a screening center designated by the government to rule out or confirm the diagnosis.

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Ontario
New Brunswick

If you have had close contact with an infected person who has tested positive, you should also be tested, even if you have no symptoms. You may receive a call from public health suggesting that you get tested. Testing may also be necessary in other situations, such as when returning from a trip abroad, or before leaving on a trip.

Anyone who tests positive should isolate themselves at home (or in some cases, at the hospital). They must notify all individuals with whom they have had close contact, and these individuals should also be tested, isolate themselves while waiting for the results, and watch for symptoms.

There are two main types of screening tests: PCR tests (molecular detection of SARS-CoV-2 genetic material) and antigenic or "rapid" tests (detection of SARS-CoV-2 proteins).

 

PCR tests

PCR tests are very sensitive and can detect the presence of the virus and therefore confirm the diagnosis of COVID-19 from the very beginning of the infection. Some of them can also identify the presence of other respiratory microbes, such as influenza. They are currently considered the reference standard. These tests must be analyzed in a designated laboratory, as they require sophisticated equipment and medical expertise.

Some PCR tests involve taking a sample from inside the nose or throat. Others use a saliva specimen (spitting into a tube) or a gargle method, but are less reliable than nasopharyngeal swabs. Results are usually obtained within 24 to 48 hours.

 

Rapid (antigenic) tests

The main advantages of rapid tests are that they are easy to use and provide a result in less than an hour. However, they are less sensitive than PCR tests: their ability to detect small amounts of virus is lower. A positive result must be confirmed by a second laboratory test.

The results of rapid tests must therefore be interpreted with more caution to avoid the impression of safety when the person is actually contagious (false negative). That said, the use of rapid tests is useful in several contexts, particularly when a large number of individuals need to be tested, when frequent testing is required or when a rapid result is needed (in an airport, a factory, etc.).  

 

Some relevant information

  • If you have a positive PCR test, a public health worker will ask you some questions about your symptoms, where you've been and what you've been doing in the last few days. They will also ask you about people you had contact with while you were contagious. This process is normal and necessary for proper action to be taken.
  • Even if you have been properly vaccinated against COVID-19, you may still get the infection (but your chances are much lower, especially of getting the more severe forms of the disease). If you have symptoms or have been in close contact with an infected person, do not take any chances and get tested if suggested.
  • Never relax health measures, even if you are vaccinated, have no symptoms or have recently tested negative for the disease.

When you get tested, you are making a difference in the fight against the pandemic. Who knows... maybe because of you, an outbreak and even deaths will be averted.

Do not hesitate to consult your pharmacist for more information about COVID-19 testing. To make an appointment for a screening test at a Jean Coutu affiliated pharmacy near you, please follow the links below based on your situation:

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COVID-19 testing: who, when and why?

COVID-19 tests are part of the arsenal available to fight the pandemic. Using them properly can save lives!
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