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Covid-19: People are not being warned about pitfalls of mass testing

BMJ 2021; 372 doi: https://doi.org/10.1136/bmj.n238 (Published 26 January 2021) Cite this as: BMJ 2021;372:n238

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  1. Elisabeth Mahase
  1. The BMJ

Only a third of local authorities that are rolling out lateral flow testing have made the test’s limitations clear to the public—including that it does not pick up all cases and that people testing negative could still be infected, an investigation by The BMJ has found.

A search of the websites of the 114 local authorities rolling out lateral flow testing1 found that 81 provided information for the public on rapid covid-19 testing. Of these, nearly half (47%; 38) did not explain the limitations of the tests or make it clear that people needed to continue following the restrictions or safety measures even if they tested negative, as they could still be infected.

Although 53% (43) did advise people to continue to follow the current measures after a negative result, only 32% (26) were clear about the test’s limitations or its potential for false negatives. The advice the websites gave to the public about a negative test result ranged from “A single negative test is not a passport to carrying on your daily life ‘virus-free’ . . . don’t let a negative covid-19 test give you a false sense of security” to “It is good news that you don’t have the coronavirus.”

On 10 January England’s health secretary, Matt Hancock, launched the drive for local authorities to test asymptomatic people who cannot work from home, to try to halt the spread of the virus.2 But many public health experts are concerned about false reassurance from mass testing.

Studies have shown that, while false positives are rare with the commonly used Innova lateral flow test, false negatives are much more common.3 Results from Public Health England showed that the test’s overall sensitivity was 76.8%, meaning that 23.2% were false negatives. Sensitivity dropped to just 57.5% when carried out by self-trained staff at a track and trace centre.

Communicating results

Margaret McCartney, a GP based in Glasgow, said, “It’s a rule-in, not rule-out test. False positives low, false negatives high. We can argue about fine print, but people need clarity about what the results mean. I think it’s important that the risk of false negatives is spelled out.” She added that local authorities should be better supported in their communication with the public.

A spokesperson for the Department of Health and Social Care told The BMJ that the government had been clear that a negative lateral flow test result did not rule out infection and that everyone should continue to follow the restrictions. The spokesperson added that the government was working to support local authorities in communicating such public health messages.

However, Mike Gill, former regional director of public health for the South East region, highlighted that the government’s community testing guidance4 for local authorities did not make the limitations clear.

He said, “It is absolutely appropriate that local authorities shape the messaging surrounding testing to suit local circumstances and cultural groups, but all messaging should fulfil basic minimum standards.

“Unfortunately, this range of approaches across the country is predictable. The recently published government guide to community testing,4 for all its length, is entirely silent on the issue of standards of messaging. The words ‘communication of results’ and ‘false negatives’ do not appear.”

Ian Hudspeth, chair of the Local Government Association’s Community Wellbeing Board, said, “We would encourage every resident to be provided with full information about the risks and benefits of lateral flow tests, prior to being tested. It is important for the public to be aware of the reliability and limitations of the use of these tests, alongside the need for continued safety measures including use of personal protective equipment, social distancing, and hand hygiene.

“We want to work with the government to reinforce this message, so that people fully understand what to consider when taking lateral flow tests.”

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