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COVID-19 testing in the United Kingdom

Date of article: 6 July 2020

Opaque reporting in the UK

Two weeks ago, I stumbled on a preview version of the new COVID-19 tracker of the United Kingdom and noticed something new: a breakdown of 'tests by type'. I was surprised to see that for weeks the UK had been including antibody testing in their reports. As I study COVID-19 reports all around the world, I had seen this before in countries like Ecuador, Peru and Senegal, but they explicitly mention they include antibody testing in every single report.

Antibody testing are being counted for the testing totals in the UK

To me this wasn't the first time to see opaque reporting on coronavirus testing by the UK government. Another example was UK stopping to report on 'persons tested'. The UK did not report on persons tested for 6 weeks, something I haven't seen in any other country. Two examples not even coming remotely close, but still the closest:

Belarus refused to report the number of new cases for 3 days and only reported on deaths. (April 19) (source)
Ethiopia is having a total internet shutdown since June 29 (due to civil unrest) and is unable to publish numbers on their websites.

However, the first time UK was unable to report on 'persons tested' was for one day only, on May 19. The reason was that the data "was affected by a technical issue with data collection systems".(source) However on May 20 the reporting on 'persons tested' was resumed and it turned out that the May 19 report which was never published (but could still be calculated) was the lowest amount of 'persons tested' in 3 weeks. Perhaps it's just a coincidence, but it did feel a bit fishy at that time.

On 19 May, the first day that 'persons tested' data was not released by the UK government, happened to be the day with the fewest persons tested.

After three more days of reporting on 'persons tested' (May 20, May 21 and May 22), the UK stopped reporting on 'persons tested' for an unprecedented 6 weeks and instead only reported on 'number of tests', which was first described as "X tests concluded", but over time was changed without explanation to "There have been X tests". Unfortunately, only now I understand why this wording matters..

Earlier description of the tests number: "tests concluded"

The new description of the tests number: "there have been X tests"

New transparency in UK reporting

As of July 4, the Department of Health and Social Care (DHSC) stopped publishing the daily number in the way they had done since the start of the outbreak. As a data analyst I want to see data with a daily freeze, so in fact the images published by the DHSC were very useful to see and retrieve historic data in the UK at any point in time. Instead, now the DHSC redirects directly to the current tracker at: https://coronavirus.data.gov.uk/

In recent weeks the UK has disclosed more information about the testing, including a testing data spreadsheet. Now we also know what was meant when the DHSC wrote "there have been X tests". It actually meant: "there have been X tests made available, but the tests have not been processed". So what does this mean? Let me give a full breakdown of the last published report on Twitter, the July 3 report.

If you would read this report in almost any other country in the world, it would mean that 10,120,276 samples have been PCR-tested. However, as mentioned above, this number includes various types of tests:

Pillar 1 and Pillar 2: 8,439,463 PCR-tests
Pillar 3: 1,123,615 antibody-tests
Pillar 4: 783,000 surveillance tests (mix of blood tests and swab tests, partially includes antibody tests)

But then we still don't have a number which we can compare with the numbers published in other countries, as the number of 8,439,463 PCR-tests consists of two groups:

A total of 6,147,681 tests processed
A total of 2,291,782 tests made available, but not yet processed

A visualization of the above breakdown would look like this:

Finally, to know how many of the current number of tests being added in the UK are in fact processed PCR-tests, we can substract recent totals. I do this below with an interval of 1 week to get more reliable information, using the increase in testing numbers between June 26 and July 3. As can be seen in the pie chart below, less than half (45.5%) of the currently reported "daily tests" are in fact processed PCR-tests.

Bar chart: less than 50% of new tests reported by the UK are in fact processed PCR-tests.

Summarized

Over the past months the United Kingdom had:

6 weeks of no reporting on 'persons tested' due to a "technical issue with data collection systems";
reported a total test number, and included antibody tests to their 'number of tests' without clearly mentioning it from the start;
reported a total test number, and included PCR tests which were 'made available' but not processed to their 'number of tests' without clearly mentioning it from the start;
many times they revised the numbers reported on testing, cases and COVID-19 tests, perhaps more than any other country in the world.

With the new information and data published, it's now easier to understand what's inside the UK data, still it's questionable the UK continues to push the inflated "number of tests" including both antibody tests and PCR tests not yet processed.

Further reading / sources:

article by Newsnodes