Testing for COVID-19: Diagnosing and how we test
On this page
- Deciding who should get tested
- How we test for COVID-19
- Tests to find out if you currently have COVID-19 (diagnostic test)
- Tests to find out if you’ve been infected by COVID-19 (antibody test)
- Re-infection and immunity
Deciding who should get tested
People with COVID-19 can have:
- mild symptoms
- severe symptoms
- no symptoms at all (also known as asymptomatic)
To decide who should be tested, health care professionals assess people based on their:
- underlying medical conditions
- risk of exposure to the virus
How we test for COVID-19
Want to understand COVID-19 testing?
Download and share the poster on testing
In Canada, there are different ways to test and analyze results for COVID-19. As laboratories and public health officials integrate new tests and technologies, they will determine the right test for you.
Currently, all tests must be performed by a health care professional. At this time, we haven’t authorized at-home test kits (where you collect the sample and do the test yourself at home).
Want to see how testing is done? Watch health professionals in action.
Tests to find out if you currently have COVID-19 (diagnostic test)
Tests such as molecular polymerase chain reaction (or PCR) tests detect the virus itself and diagnose COVID-19. If you’re being tested for a possible current case of COVID-19, you’ll receive one of these tests.
How samples are collected
There are different ways samples can be collected to test for COVID-19. Samples can be collected through a:
- nose swab
- throat swab
- saliva sample
How samples are tested to detect the virus
For laboratory-based testing, such as molecular PCR:
- samples are sent to a laboratory for analysis
- results are generally provided in 1 to 3 days
For point-of-care testing:
- sample collection and testing is done at the time and place of care, such as a hospital or doctor's office
- results are provided while you wait
Point-of-care technology can only test a limited number of samples in a single machine. Because of this, it's used in places where it's needed most, including:
- rural, remote and isolated communities
- specific high-risk settings where it's important to have fast test results without having to send samples to a laboratory
A positive laboratory-based or point-of-care test means that you currently have COVID-19.
Tests to find out if you’ve been infected by COVID-19 (antibody test)
Antibody (serology) tests use a sample of your blood to check for antibodies. Your body makes these after it's exposed to the virus.
A positive serology test means that, at some point, you were infected by the virus. But it can't tell how long ago you were infected.
Serology tests aren't used to diagnose COVID-19 in early stages of infection, since they don't detect the virus itself.
Serology tests can help:
- estimate how many people have had COVID-19
- better understand how much the virus has been spreading in the community
- determine which public health measures need to be in place
On April 23, 2020, Canada launched the COVID-19 Immunity Task Force to lead a Canada-wide unified effort to perform serological tests. To determine the groups of Canadians who will receive serology testing as a first priority, the task force is coordinating with:
- provinces and territories
- research groups
Re-infection and immunity
We’re aware that other countries are reporting re-infection cases from different strains of the virus.
We don’t yet know if those who have recovered from COVID-19 are safe from re-infection. Other respiratory viruses generally don’t provide people with 100% immunity after recovery, so it’s important to determine:
- how long protection lasts
- whether it’s possible for individuals to experience less severe or potentially more serious illness if they get COVID-19 a second time
Canadian scientists are working to:
- assess if those who have recovered from illness are safe from re-infection
- understand how the immune system reacts to the virus
- understand the rate and consequences of re-infection
COVID-19 re-infection is hard to confirm. This is because people may continue to test positive by PCR for several weeks or, more rarely, months, after recovery. Specialized testing is usually required to confirm re-infection from different strains of the virus. Researchers need to analyze the virus’ complete genetic material.
There remains much uncertainty around possible re-infection. Those who have recovered should take the same actions to prevent COVID-19 as someone who has never had the infection.
Report a problem or mistake on this page
- Date modified: