Statistics chief criticises Covid-19 test figures

The UK's chief statistician has criticised the government for presenting misleading and unclear figures about its progress on testing for Covid-19.

In a letter to Health Secretary Matt Hancock, David Norgrove, chair of the UK Statistics Authority, said the government was mixing up tests carried out with test kits sent out by post and under-presenting the number of positive tests. His letter, dated 2 June, is the second time Norgrove has asked the government to improve its reporting.

Norgrove said test figures had two main purposes: to understand the epidemic and to help manage the test programme so the public knows how effective it is.

"The aim seems to be to show the largest possible number of tests, even at the expense of understanding," Norgrove wrote. "It is also hard to believe the statistics work to support the testing programme itself. The statistics and analysis serve neither purpose well."

Norgrove said the difference between tests carried out and posted out was "too often elided" at the daily Covid-19 press conference to represent tests undertaken. There are no figures on how many tests posted are carried out, he said.

The summary of statistics also shows positive results from diagnostic tests next to the total number of tests. "This presentation gives an artificially low impression of the proportion of tests returning a positive diagnosis," Norgrove said.

The daily slides do not say how many people have been tested more than once and figures for the overall number of people tested are not available, Norgrove said. He also said testing figures were difficult to understand and that many of the the important numbers made little sense without checking hard-to-follow notes.

"It is not surprising that given their inadequacy data on testing are so widely criticised and often mistrusted," Norgrove said. His second letter goes over much of the ground covered in his letter of 11 May, to which Hancock said he would make the programme "as transparent as possible"

Norgrove also called on the government to:

• show results for types of employment, age, sex and location to show how people in certain circumstances were affected
• come up with key metrics for the test and trace programme to avoid the failures of the testing scheme.