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Covid-19: Leading statistician welcomes UK government’s move to improve testing data

BMJ 2020; 369 doi: https://doi.org/10.1136/bmj.m2175 (Published 01 June 2020) Cite this as: BMJ 2020;369:m2175

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  1. Abi Rimmer
  1. The BMJ

A leading statistician has welcomed an announcement by the government that it is changing the way it reports covid-19 swab test results.

On 11 May David Norgrove, chair of the UK Statistics Authority, wrote to Matt Hancock urging the government to make its data on the national covid-19 testing strategy clearer.1 In his reply to Norgrove, sent on 27 May, the health secretary said that developments to improve data reporting were already under way.2

He said that the government had published a clear definition of how the target to perform 200 000 tests a day by the end of May would be measured and reported. “Capacity will be measured across testing pillars 1, 2, 3, and 4 by asking laboratories each day to set out how many tests they can provide,” Hancock said. From 27 May the government will publish weekly data3 and commentary on this target, he said.

Department of Health and Social Care figures on the number of patients who have been tested for coronavirus and the number of positive tests is broken down into categories with daily reports for pillars 1, 2, and 4 (see box). The government is also simplifying how it presents the daily figures on tests and making the figures easier to find, Hancock said.

He wrote, “We are reducing the volume of detailed technical comment each day but will complement this with a detailed note on methods that will also detail any revisions or updates to the figures. This will explain the various strands of testing and will also set out how each strand is counted and reported.”

The government is also publishing a time series of data,4 with more detail than the current daily totals, “setting out clearly how this has grown over time and making it clear when new strands of testing were added in,” Hancock said.

He added, “It is not straightforward to provide a definitive geographical breakdown of these figures, but I want to ensure we provide as much detail as possible for those using the statistics, and we will continue to develop that analysis.”

Sheila Bird, former programme leader at the MRC Biostatistics Unit, Cambridge Institute of Public Health, said that she was particularly encouraged by Hancock’s statement that the government was “reconciling [its] approach to reporting across the different testing pillars to ensure consistency,” which, she said, would put the figures “on a firmer and more consistent footing.”

Bird, a member of the Royal Statistical Society’s covid-19 taskforce, said that the promised weekly reports had the potential to be more useful than the daily testing data that was previously shared. The health department has recently been criticised for not sharing certain testing data in its daily announcement.567

Since 23 May its daily coronavirus announcement on Twitter8 has not included figures for the number of people tested. In its tweets, the department said that this was “to ensure consistent reporting across all pillars” and was because some people in pillar 2 are tested more than once.

But Bird said that an overall number of people tested was not particularly helpful. “I’m not interested in an overall number, I’m interested in the different categories of people who have been tested, so I can get at a like with like comparison over time.”

She added that it was surprising that the health department was only now explaining that some patients might have been tested more than once. “It’s pretty obvious that that’s how things have to work in hospitals,” she said.

Pillars of testing

Pillar 1: Swab testing in Public Health England labs and NHS hospitals for people with a medical need and for the most critical workers and their families

Pillar 2: Swab testing for key workers and their households

Pillar 3: Mass antibody testing to help determine whether people have immunity to coronavirus

Pillar 4: Surveillance testing to learn more about the disease

References

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