Rapid Covid testing in England may be scaled back over false positives

[Northerner]

Senior government officials have raised “urgent” concerns about the mass expansion of rapid coronavirus testing, estimating that as few as 2% to 10% of positive results may be accurate in places with low Covid rates, such as London.

Boris Johnson last week urged everyone in England to take two rapid-turnaround tests a week in the biggest expansion of the multibillion-pound testing programme to date.

However, leaked emails seen by the Guardian show that senior officials are now considering scaling back the widespread testing of people without symptoms, due to a growing number of false positives.

In one email, Ben Dyson, an executive director of strategy at the health department and one of Matt Hancock’s advisers, stressed the “fairly urgent need for decisions” on “the point at which we stop offering asymptomatic testing”.

Rapid Covid testing in England may be scaled back over false positives

Exclusive: In leaked emails, Matt Hancock’s adviser says there is ‘urgent need for decisions’ on asymptomatic testing

www.theguardian.com

That went well... 🙄

 

[Bruce Stephens]

Senior government officials have raised “urgent” concerns about the mass expansion of rapid coronavirus testing, estimating that as few as 2% to 10% of positive results may be accurate in places with low Covid rates, such as London.

I think the regime should go through the national screening committee rather than arbitrarily being launched (perhaps because we've bought warehouses full of tests?). But 2-10% seems a bit low.

Covid: 82% of positive rapid tests 'were correct'

There had been concerns that large numbers would have to self-isolate after a false positive result.

www.bbc.co.uk

 

[Amity Island]

Senior government officials have raised “urgent” concerns about the mass expansion of rapid coronavirus testing, estimating that as few as 2% to 10% of positive results may be accurate in places with low Covid rates, such as London.

I was astonished when I heard they were planning random testing, goes against everything they have been telling us.

They know full well testing randomly will produce high numbers of false positives. You are supposed to use the test on people who have symptoms to verify they have covid, not just on random people without any symptoms.

"With a false positive rate of 0.8% - a figure used by Ms Hartley-Brewer and within the broad range of what we think might be the actual rate for community testing - you would get eight false positives. So in that context, it's true that roughly 90% of positives would be false."

Coronavirus testing: What is a false positive?

Some commentators say rising cases are just because of false positive results. But that's not true.

www.bbc.co.uk

At airports (asymptomatic people) only 7% of tests give an accurate result

Which I assume applies to all the other tests done on asymptomatic people? Like the ones asked to test in areas under lockdown?

forum.diabetes.org.uk

 

[mikeyB]

The more tests you do, the more false positives you will get. So what. It’s the false negatives I worry about.

 

[Bruce Stephens]

Professor Oliver Johnson still doesn't see how they get 2-10%:

https://twitter.com/x/status/1382942209310404608

 

[Amity Island]

The more tests you do, the more false positives you will get. So what. It’s the false negatives I worry about.

Doing more tests is not an issue, it's doing more tests on those without any symptoms or infection.

How are we going to get out of this mess if these "cases" on random people are false "cases". We've been locked down based on the number of positive tests. We certainly don't need any deliberately targeted false positives.

 

[mikeyB]

We wouldn’t necessarily get locked down - every positive test has to be followed up with a proper blood test. If that’s negative, no worries.