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A graph comparing rapid antigen testing and PCR testing for probability of detecting SARS-COV-2 based on viral load across time since exposure. A marker showing the onset of symptoms occurs before both tests reach maximum probability of detection.

Different tests, different purposes

There are many different types of tests that are being used for different purposes, each with different purposes and each with a role to play in getting people back to living. 

Antibody Tests:  Best for understanding where the virus has been

Antibody tests use a sample of blood to detect antibodies which your body creates after you have had COVID-19.  Antibody tests answer the question “Have I had COVID-19?”  Antibody tests are not used to determine if you currently have COVID-19 because they are not testing for the virus itself.  These tests are being used for public health surveillance to better understand what populations have been most affected. It’s not known yet whether the presence of antibodies means that you are immune to the virus and scientists are continuing to study this.

PCR Tests: Best for diagnosing COVID-19

PCR tests are considered to be the gold standard for diagnostic testing.  They answer the question:  “Do I have COVID-19?” They track the presence of genetic material that is left behind by the COVID-19 virus and can detect the material long after contagiousness. They are highly accurate but expensive and time consuming when compared to the other tests that are available.

Recent guidance from the Ontario Ministry of Health says that symptomatic people should get tested via PCR tests at a public health facility, taking the proper precautions to self-isolate until the lab-based test results are known.

But 1 in 3 people who have COVID-19 are asymptomatic.  They are carriers and can spread the virus unknowingly.  This is where the next type of test comes into play.  

Antigen Tests: Best for screening for contagiousness

Antigen tests detect the presence of the COVID-19 virus and can provide results within 15 minutes. They are most effective when viral loads are the highest, which is the 7-10 days when the virus is most likely to be transmitted. In other words, antigen tests are best used to answer the question “Am I contagious?”

Stopping the spread via screening is the main goal of the antigen test.  That’s why Canada, the US, England, Germany, Switzerland and others have made antigen tests an important part of their strategy to manage COVID-19.  

It’s the immediacy and frequency of the rapid antigen test that allows for COVID-19 to be detected when it is most infectious.  Immediate results mean faster contact tracing and quarantining. In fact, Ontario Health suggests that people should be using antigen tests 2-3 times a week in red zones, and 1-2 times a week in every other zone. 

Screening tools work best when everyone has ready access to them. In the UK, home testing kits are available to any citizen. In the US, home kits can be purchased over the counter at pharmacies and grocery stores. Until recently, tests have only been available to small and medium sized businesses in Ontario.  

We’re proud to be providing amongst the first antigen tests that are available to everyone.