Conducting COVID-19 PCR Testing at PHO
PCR testing (also known as polymerase chain reaction testing), is a type of test that tells us if someone currently has COVID-19. This is in contrast to serology testing, which tests someone’s blood to see if they have generated antibodies in response to COVID-19 infection, this primarily 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 cannot be copied, there is no virus in the sample, or there is such a low amount that even this very sensitive test cannot 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.
- Positive COVID-19 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 with instructions on how to self-isolate and interviews them to inform contact tracing efforts.
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.
PHO Rounds: International Border Surveillance Study
Arriving international passengers at Toronto’s Pearson International Airport were enrolled in a prospective study of COVID-19 risk upon arrival and during quarantine in September and October 2020.