Sask. working to identify best version of antibody testthat could measure public COVID-19 immunity

Work is underway to identify the best version of a test that could determine if a person has had COVID-19 by searching forantibodies in their blood.

Known as serology testing, the method can ascertain if a person was ever infected by looking for the specific antibodies that would be produced in response to the virus.

Only one version of the test has been approved for use by Health Canada to date, but the Roy Romanow Provincial Laboratory in Regina and Royal University Hospital in Saskatoon are also testing others to assess their effectiveness.

Of the 1,000 tests Saskatchewan has on hand for the purpose of experimentation, 300 are the DiaSorin LIAISON approved by Health Canada.

Once a test is chosen and validated, "we would scale up how much we have on hand," said Dr. Amanda Lang from the Roy Romanow Provincial Laboratory.

She said evaluating each test involves investigating how specific and sensitive the results are, as well as how accurate it would be.

Lang said the lab endeavours to answer those questions using samples.

"We need to have serum samples from patients who are known to have had COVID-19 and from patients who are known to not have been infected, as well as from patients who are known to have had disease from similar viruses," like those that cause the common cold, to ensure the test isn't producingfalse negatives or false positives, she said.

Measuring immunity

Dr. Saqib Shahab, chief medical health officer for Saskatchewan, said last month that serology tests will help measure the level of COVID-19 immunity in the community, because some asymptomatic cases may never be found through other methods.

He said it could be months before such tests become available for public use.

"Once the serology test is used to measure the level of immunity in the population, that will be one good thing to re-confirm ... our estimates of how much COVID-19 transmission has happened," he said.

"Is that confirmed by serology, or does that show that transmission is a bit higher?"

He said the biggest question will be how much protection a person will have from getting reinfected if they have had COVID-19 in the past.

"If you were never diagnosed with COVID or did have COVID in the past, what does the serological test tell you in terms of your current immunity, and how long does that immunity last?"