COVID-19 Laboratory Testing in Ontario

Laboratory testing is an essential component of Ontario’s response to COVID-19. Not only because it tells us if someone has COVID-19 or not, but also because it sheds light on where and how the virus is spreading.


PHO’s laboratory conducts over 6 million tests every year at our 11 sites across Ontario on a broad range of clinical and environmental samples – operating one of the largest public health laboratory systems in the world.

Laboratory testing is an essential component of Ontario’s response to COVID-19. Not only because it tells us if someone has COVID-19 or not, but also because it sheds light on where and how the virus is spreading.

PHO performs thousands of COVID-19 tests every day in partnership with many hospital, academic and private labs across the province. This network of labs, coordinated by Ontario Health, has come together rapidly since early 2020, in order to meet the increased demand for testing. Find out more about the early days of COVID-19 testing in Ontario.

In addition to performing tests, PHO acts as Ontario’s reference laboratory for COVID-19 testing. This means that we provide support to new labs as they come online with testing and also validate early samples from those labs to confirm the accuracy of the testing. We also validate new test methods (in collaboration with partner labs, including the National Microbiology Lab) and provide expertise to inform the evolution of Ontario’s testing strategy, including how these new methods are implemented.

Health Care Providers

See our COVID-19 Test Information Sheet for details about collecting and submitting a sample and our COVID-19 Laboratory Testing Frequently Asked Questions.

How is testing for COVID-19 done?

The current method used in Ontario to test for COVID-19 is called PCR testing. Also known as polymerase chain reaction. This type of test tells us if someone currently has COVID-19, unlike testing someone’s blood to see if they have antibodies for COVID-19, which tells us if someone previously had COVID-19. Find out more about the difference between these two types of tests and their application.

PCR testing is performed in the lab to help us find even tiny amounts of the virus. It does this by amplifying a virus’ genetic material to a level where it can be detected. The test requires a sample from a person. This sample is collected by a health care provider, typically using a swab inserted into a person’s nose or throat.

The Journey of a COVID-19 Sample Tested at PHO

  • Once we receive a sample, the information about the sample and the patient is entered into our laboratory information system (LIS) for tracking.
  • Then, a technologist uses chemicals (referred to as “reagents”) and equipment to extract the genetic material from the sample collected on the swab.
  • That extracted material is then placed into a tube which contains new reagents.
  • That tube is placed in a machine that can run tests on many tubes at once. This machine enables the PCR “reaction” to make millions of copies of a piece of the viral DNA. This process is called “amplification”.
  • This amplification process allows even a small amount of virus to be detected if it is present in the sample.
  • If the piece of DNA can’t be copied, there is no virus in the sample, or there is such a low amount that even this very sensitive test can’t detect it.

What happens after the test is done?

  • The results are entered into our LIS and the health care provider who ordered the test is sent the result.
  • The person who was tested is then informed of their results by the doctor (or the institution that ordered the test), or gets their results from the Government of Ontario’s results portal. For privacy reasons, PHO does not provide test results directly to patients.
  • For COVID-19, positive results are also sent to the local public health unit for the area where the sample was taken. The health unit follows up with the person who has tested positive to provide them instructions on how to self-isolate and interviews them to inform contact tracing efforts.

Who should be tested for COVID-19?

The Ministry of Health develops testing guidance for COVID-19 that is updated as the outbreak continues to evolve and laboratory testing capacity increases.

PHO does not currently recommend routine testing of asymptomatic persons for COVID-19 (outside of those recommended in the guidance from the Ministry of Health, or as directed by the public health unit for public health investigation). However, clinicians should continue to use their discretion to make decisions on which individuals to test.

If you are concerned that you may have been exposed to, or are experiencing symptoms of COVID-19, please visit the Ministry of Health website, take their self-assessment and follow their guidance and instructions. If you are having difficulty breathing or experiencing other severe symptoms, call 911 or go to a hospital emergency room immediately.

Adapting to Future Needs

We work with Ontario Health and other key experts and stakeholders to monitor, provide guidance, and strategize to make sure testing in the province continues to respond to this evolving public health emergency. We explore new test methodologies, like serology, and continue to investigate and validate the use of different types of swabs, reagents, and testing platforms so that our approach can be flexible.

Updated 14 June 2020