Is the UK performing 240,000 Covid-19 tests per day?

The Claims

"We're now doing about 240,000 antigen tests a day, at the moment… 240,000 is the latest figures… This is the capacity in the system." Nadhim Zahawi MP, 17 September 2020

"The government's own figures, the latest figures, are that 81,000 people are being tested every day. That's the government's latest figures. Not 240,000. 81,000." Fiona Bruce, 17 September 2020

It appears to be a general confusion around the difference between the number of people being tested for Covid-19 and the number of tests that are actually available or performed.

Many influential figures in the media and politics are wrongly comparing the number of people newly tested in England(weekly reported in Test and Trace statistics) with either the testing capacity for the entire UK or the number of tests conducted (both from the Coronavirus Dashboard).

Crucially, the figure for those "newly tested" won't include most people who've been tested more than once since the Test and Trace system started running.

This error appeared in the Sunday Times, Angela Rayner repeated it during Prime Minister's Questions on the following Wednesday, and Fiona Bruce during Question Time on Thursday. Ms Bruce's mistake was then made by Femi Oluwole, and other influential Twitter users.

In Parliament, Jacob Rees-Mogg MP also mixed tests carried out with people tested when he stated that, "almost a quarter of a million people per day can get tested".

The real figure for how many people are tested for Covid-19 in the UK each day is not known. That is because the government does not publish it. The Department for Health and Social Care also has not provided this figure.

What are they getting wrong?

At the moment, there is more demand for Covid-19 tests in the UK than the system can meet.

The official Coronavirus Dashboard issues a "lab capacity" figure, which states the number of tests the labs can process per day. It also gives a "tests processed" number, which attests the number of tests they process.

Even at this time of excess demand, labs have processed as many Pillar 1 and 2 tests per day as expected to be able, only once. (Pillars 1 and 2 of the testing system are those that involve swab tests to see whether someone is presently infected with the virus, and account for the majority of tests carried out.)

This suggests that the capacity figure may not tell us how many tests can occur in practice. The government itself also recognises that "operational issues can result in labs performing below capacity".

The highest number of tests processed in a single day was, on 12 September, 238,640. Therefore Mr Zahawi's figure was broadly correct (although the latest figure for tests processed is a little lower, at 223,146). The most recent figure for claimed capacity is just over 240,000.

However, this does not mean we should expect to test 240,000 people, because some people, for a variety of reasons, are tested more than once. (For instance, Public Health England is now recommending to test a second time all borderline positive cases ).

The fact that the number of tests is different from the number of people tested is not a new issue.

What we don't know is the number of tests being carried out on average for each person tested, because the government doesn't issue figures that would allow us to work that out.

Currently, there is no national figure for the total number of people tested every day either. The closest thing we actually have is the number of those "newly tested" every week in England, which is issued by the Test and Trace statistics. This was 571,400 in the figures for the week up to 9 September, which works out about 82,000 per day.

This figure only covers England. It does not include those who were tested in Scottland, Wales or Northern Ireland. And because it only counts people who were newly tested in that week, it also probably misses most people who have been tested before—for instance, frontline health workers, or staff and residents in the care homes. (An exception for those who result to be positive the first time after their test had come back negative before. These people are moved to the week when they first tested positive.)

Until we have the right data, knowing how much difference it would make if we included all these people is not possible. The UK's testing system might be testing only a bit more than 82,000 people each day—or many more. We simply don't know.

Currently, what we can say is that the "tests processed" or the "testing capacity" with the "people newly tested" figures cannot be compared, because they measure different things.