An update on antibody testing for COVID-19

Since Health Canada approved the first serological test that detects antibodies specific to COVID-19 in May, many Canadians are wondering when they will be able to receive a test.

Here’s a review of what exactly antibody tests are as well as the latest update on where British Columbia and Alberta are at in ensuring safe and effective antibody testing for the public.

What is antibody testing?

Antibody, or serological tests, do not detect the virus itself. Instead, they check for past immune exposure (antibodies) to COVID-19. The test may determine if a person has previously been infected with COVID-19. This is in comparison to the viral tests that are currently available that are used to determine whether a person has an active COVID-19 infection. Antibody tests are also different from the viral tests in that they require a sample of blood to complete the test.

An antibody test is important because people with antibodies may have some protection against COVID-19 (although research is still ongoing to determine this).

The demand for antibody testing is understandably high. Up to 30% of people infected with COVID-19 do not show symptoms and most other cases will have very mild symptoms that make it difficult to determine whether you have COVID-19 or simply a mild cold or an upset stomach. It’s no wonder why people are curious as to whether or not they unknowingly had COVID-19 and may have developed some sort of immune resistance to the virus. With that being said, there are a few reasons why the tests have not been rolled out to the Canadian public as of yet.

The latest on antibody testing in British Columbia and Alberta

While Health Canada has approved several antibody tests, the British Columbia Centre for Disease Control (BCCDC) and Alberta Health have not.

Researchers in B.C. and Alberta are still studying antibody tests to determine whether they are useful for people in their respective provinces. At this time, both provincial health authorities are using the tests to get an idea as to how many of the local population have been impacted by COVID-19. A study carried out by the BCCDC, University of British Columbia (UBC) and LifeLabs in mid-July tested samples from a random group of people who were already getting blood tests in March for other reasons. The study estimated that eight times as many people had been sick with COVID-19 than officially confirmed, but also found that less than one percent of the province’s population had antibodies.

The results of this study are significant because such a low prevalence rate of COVID-19 in a population, as is the case in B.C. and Alberta, can lead to a high percentage of false positive antibody tests. In this case, a false positive test would incorrectly inform an individual that they have antibodies, when in fact they do not. Since such a large percentage of the population in B.C. and Alberta have not had COVID-19, the likelihood for a large number of false positive tests would be significant. For now, provincial health authorities are using antibody tests to influence population-based decisions.

The following graph highlights the risk of false positive tests with a low prevalence of COVID-19 (please note, the numbers provided in the graph are given as an example. The exact prevalence rate, sensitivity and false positive rate for the antibody test is still being determined).

*Graph provided by Lucas Wheeler

In addition to the false positive tests, there are still many unknowns when determining the results of an antibody test. Health Canada is still trying to determine whether people with antibodies are immune to re-infection or if they are still infectious to others.

Other factors may influence the results of an antibody test as well. For example, antibody testing in elderly or immuno-compromised people is unknown because there age or condition can have an impact on their body’s immune response. We’re also not sure how long COVID-19 antibodies are present for after an infection has ended. Similarly, an individual who unknowingly has COVID-19 or recently had COVID-19 might test negative for the antibodies when their body just hasn’t developed them yet.

Can I receive an antibody test?

Not yet. Until researchers learn more about the antibody test and the BCCDC and Alberta Health approve the tests, they will not be available.

Please be assured that Copeman Healthcare and TELUS Health are actively pursuing antibody testing strategies. As soon as we have more information regarding these tests we will share it with you.