N.B. COVID-19 wastewater data restored to national site after quality review over accuracy

The Public Health Agency of Canada has restored COVID-19 wastewater data for New Brunswick on the national COVIDwastewater website, following a five-month "quality review" related toconcerns about the accuracy of test results.

The agency's national microbiology laboratory "wanted to assess the batch-to-batch variability" and sensitivity of the testing cartridges used in New Brunswick'sGeneXpert system a polymerase chain reaction rapid-testing platform for infectious diseases, said spokespersonAnna Maddison.

"Different batches of cartridges may have differences in performance and this can affect the test accuracy, sensitivity and specificity," she said in an emailed statement.

"Prior to publishing data from a different batch of cartridges, the [national microbiology laboratory]conducted a quality review to ensure the cartridges were reporting accurate results."

Maddison did not respond to questions aboutwhat prompted the review, which started in April and included testing "contrived and authentic" wastewater samplesand "assessing quality metrics."

But "there were no identified issues with the new test lot."

The lab "temporarily paused" publishing data for all 10 New Brunswick testing siteson the federal dashboard untilSept. 20, after the review was completed, "out of an abundance of caution."

As of Tuesday's update, COVID activity in the province is high, based on the 10 sites that submit wastewater samples, representing 39.5 per cent of the population.Eight sites have a highviral activity level, Campbellton islisted as "moderate,"and no data is available for St. Stephen, with its last sample taken onAug. 11.

Across Canada, COVID activityis "moderate," according to the dashboard.

When asked whether the national lab has had to pause reporting COVIDwastewater data or conduct quality reviews for other provinces or territories, Maddisonnoted reporting of Saint John data was paused for several months last year during a quality reviewover concerns of the accuracy of its data. Officials believed samples were being drawn from a treated area and that the reported values were "not reflective of the community burden."

"It is generally uncommon for the [national lab] to pause testing," she added.

New quality controls being established

No changes were made to New Brunswick'spublished data as a result of the review, saidMaddison.

However, "additional quality controls are currently being established to allow for the efficient validation of new GeneXpert test lots without disruption to routine testing and reporting."

The Department of Health declined a request for an interview or more information. Spokesperson Katelin Dean said the COVID-19 wastewater surveillance dashboard "is the responsibility of the Public Health Agency of Canada. Questions about the dashboard should be directed to PHAC."

There were no disruptions to New Brunswick sampling during the quality review, said Maddison. The national labcontinued to receive data from the province, whichhas now been made public.

In the Saint John situation,national lab and New Brunswick scientists worked with local wastewater treatment personnel "to revise and refine the technical approach" to Saint John testing "to find a method that is sensitive and specific to their sewage treatment processes," and that data was restored in September 2023, Maddisonpreviously told CBC News.