NWT mine lab promises improvements after Covid-19 false positive

The group running Covid-19 testing for two NWT diamond mines on Tuesday acknowledged responsibility for last week’s false positive mix-up at the Gahcho Kué mine.

Tests on workers at Gahcho Kué, which is run by De Beers, are processed in a laboratory at the neighbouring Diavik mine, majority owned and operated by a Rio Tinto subsidiary.

The Diavik lab is run by a public health research and development not-for-profit named Guard, also known as GuardRX.

In an email to Cabin Radio and the CBC, Guard founder and chief executive Gary Kobinger said one of his group’s technicians was responsible for a labelling error that caused a form of false positive to be reported.

Ultimately, one new case of Covid-19 – not including the false positive – was identified and confirmed at Gahcho Kué last week.

Kobinger said the false positive came about when a Guard technician mislabelled a tube containing a positive sample, confusing it with a neighbouring tube containing a negative sample.

That meant the samples were wrongly reported and led to a subsequent negative result, “triggering a lab investigation to find out the source of the discrepancy.”

Kobinger said: “It is, in laboratory language, actually not a false positive but rather a positive that was mislabelled – or misidentified.”

He said this was the first such labelling error in 53,000 tests that have passed through Guard’s labs in the past four months.

“The investigation put light on the mistake, which was communicated immediately to all involved,” he said – though the error appears not to have been caught until the NWT government had published an initial advisory.

Kobinger said the lab would now ensure “a second pair of eyes will be double-checking” each test, while internal measures to confirm positive tests will be ramped up.

Guard’s mistake, coupled with the territorial government’s publication then retraction and amendment of an advisory regarding a separate case on Tuesday, created a confusing seven days for NWT residents.

As things stand, there have been nine confirmed Covid-19 cases in the territory. As of 7pm on Tuesday, an additional case in Inuvik remains a presumptive positive. If confirmed, it would be the NWT’s 10th.

“We have been doing diagnostic in remote areas, mainly Africa, for about 20 years,” Kobinger wrote, “and we have seen one mistake per 5,000 samples during Ebola outbreaks – more difficult conditions by far, of course.

“That said, even one out of 53,000 is one too many and we need to get to zero – even if humans are humans, and fatigue is currently a huge challenge to factor in.”

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Correction: October 27, 2020 – 21:36 MT. This article initially suggested Gary Kobinger had referred to 53,000 Covid-19 tests at Guard’s Diavik laboratory over the past four months. Diavik itself says nowhere near that many tests have been completed at the mine. It’s believed Kobinger was referring to the total for Guard’s Canadian labs, and this report has been updated accordingly.