Delays in COVID-19 testing in England

Alastair Grant, School of Environmental Sciences, University of East Anglia, UK

20th April 2021 (although the graph will normally be updated each day include that day's testing data)

In September and October 2020 there were concerns about the accessibility and turnaround times of COVID tests.  Some of the problems seem to have been related to lab capacity.  In mid-September, backlogs of unprocessed samples built up, and limits were placed on the number of testing slots made available to try to control this, leading to people being offered testing slots in locations that were sometimes several hundred miles away.  We can track how well the testing system is working by looking at how long it takes from a specimen being taken at a testing centre to the result being added to the national Coronavirus dashboard. This is updated at around 4 pm every day and reports test results entered into the national computer system by 9 am that day. Detailed data on individual cases are released to Local Authorities at about the same time.  A few of the swabs taken on Monday will be processed very quickly and reported on Tuesday. But most should be reported on Wednesday.

The graph shows the number of cases from specimens taken two days ago divided by the number of cases reported today. If case numbers are not changing, this figure will be equal to the proportion of specimens taken two days ago that have been reported by today.

Turnaround times fluctuate, but an average of around 80% of cases are now being reported within 2 days. However, this figure fluctuates substantially from day to day, and is sometimes greater than 100% as a result of variations in numbers of tests taken on different days of the week and because there is often a spike in lateral flow test results on school children at the beginning of the week reflecting tests taken in schools on Mondays and tests taken at home on Sunday evening.

COVID-19 cases in England from the past two days as a percentage of cases reported today

Percentage of tests reported within
      48 hours
You may also be interested in my analyses of daily COVID-19 data, which identifies areas with unusually high case numbers and also gives a daily rate per 100 000 and number of cases over the past week for all lower tier local authorities in England.