Intended for healthcare professionals


Covid-19: Mass testing is inaccurate and gives false sense of security, minister admits

BMJ 2020; 371 doi: (Published 18 December 2020) Cite this as: BMJ 2020;371:m4916

Read our latest coverage of the coronavirus outbreak

  1. Elisabeth Mahase
  1. The BMJ

Mass testing of people without covid-19 symptoms is “not an accurate way of screening the general population,” a senior figure at the Department of Health and Social Care has said in a letter seen by The BMJ (see Related content).

The comments were made by James Bethell, one of England’s health ministers, in response to a letter from an MP raising concerns about blanket polymerase chain reaction (PCR) testing on behalf of a constituent.

In his letter Bethell stated that “swab testing people with no symptoms is not an accurate way of screening the general population, as there is a real risk of giving false reassurance.” He added, “Widespread asymptomatic testing could undermine the value of testing, as there is a risk of giving misleading results. Rather, only people with covid-19 symptoms should get tested.”

The comments were made as the government expanded mass testing of asymptomatic people after a pilot scheme in Liverpool and announced a further rollout of widespread testing in schools.

Swabs are used both for PCR tests and for rapid tests that have been deployed by the government for mass testing in Liverpool and care homes and do not need to be sent to a laboratory for results. One of the main rapid tests used is the Innova Lateral Flow SARS-CoV-2 antigen test, which involves a self-administered swab. However, data released from the Liverpool pilot programme showed that this test detected just 48.89% of covid-19 infections in asymptomatic people when compared with a PCR test.1

When questioned about the letter a spokesperson for the Department of Health and Social Care told The BMJ, “The government is committed to using lateral flow tests in community testing to break the chains of transmission among those with asymptomatic infection . . . The minister’s letter was in reply to a specific question about ‘blanket PCR testing,’ and it remains the case that PCR testing is prioritised for symptomatic testing.”

Less accurate

However, experts have argued that it does not make sense that lateral flow tests—which are far less accurate than PCR tests—are considered good enough for mass asymptomatic testing, while PCR testing is being avoided because of its potential for false reassurance.

Jon Deeks, professor of biostatistics at the University of Birmingham and leader of the Cochrane Collaboration’s covid-19 test evaluation activities, said, “There are particular concerns about false reassurance. It doesn’t make sense that the government is concerned about false reassurance for PCR tests but not lateral flow tests.

“Lateral flow tests are going to give more false reassurance than PCR testing, because they are less accurate. It’s good to see the government is concerned about false reassurance, but haven’t they got this the wrong way around?”

Mass testing has been used at universities throughout England to help keep the virus under control on campuses. Most programmes use lateral tests, although some, such as Cambridge University, have used PCR tests.

Mike Gill, former regional director of public health for the South East England region, said, “This letter has emerged as [the education secretary] Gavin Williamson has announced the introduction of widespread testing in schools with the statement, ‘This expansion of testing into schools and colleges will ensure more certainty for children and parents and everyone working so hard in education.’

“Williamson’s statement was bad enough on its own, since it comes across as yet another egregious display of not being guided by science. The last thing anybody should be encouraged to entertain after an Innova test result, whether positive or negative, is certainty, let alone ‘more’ of it.

“Put alongside the very welcome position taken by Lord Bethell in his letter, it becomes impossible to use the word ‘coherent’ in the context of current government approaches to policy development and implementation.”

The BMJ did not receive a response to a request for clarification from Lord Bethell.


  • Correction: We amended paragraphs 3 and 5 this article on 18 December 2020 to make clear that rapid lateral flow tests are a type of swab test. On 21 December we posted a redacted version of James Bethell’s letter alongside the article.

This article is made freely available for use in accordance with BMJ's website terms and conditions for the duration of the covid-19 pandemic or until otherwise determined by BMJ. You may use, download and print the article for any lawful, non-commercial purpose (including text and data mining) provided that all copyright notices and trade marks are retained.