© Ian West/PA
English National Opera members take lateral flow tests before rehearsals.
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 health secretary Matt Hancock's advisers, stressed the "fairly urgent need for decisions" on "the point at which we stop offering asymptomatic testing".
On 9 April, the day everyone in England was able to order twice-weekly lateral flow device (LFD) tests, Dyson wrote:
"As of today, someone who gets a positive LFD result in (say) London has at best a 25% chance of it being a true positive, but if it is a self-reported test potentially as low as 10% (on an optimistic assumption about specificity) or as low as 2% (on a more pessimistic assumption)."
He added that the department's executive committee, which includes Hancock and the NHS test and trace chief, Dido Harding, would soon need to decide whether requiring people to self-isolate before a confirmatory PCR test "ceases to be reasonable" in low infection areas where there is a high likelihood of a positive result being wrong.
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