Coronavirus test results taking up to 48 hours risk rendering track and trace useless, experts warn

Coronavirus tests taking longer than 48 hours to provide results risk rendering the track and trace system useless, experts have warned.

Up to 20,000 coronavirus tests a day are taking longer than two days to provide results. Scientists advising the Government on track and trace predict this could lead to a 50 per cent increase in the number of infections.

It comes as a former director of the World Health Organisation called for GPs to be drafted in to help lead the NHS test and trace system, with testing hubs at local surgeries.

Officials are unable to say how many tests have been completed within the optimal 24 hours which has been recommended by the Scientific Advisory Group for Emergencies (SAGE).

However, the Prime Minister has admitted that 10 per cent of tests, for which they have a target of 200,000 a day, are not being completed within 48 hours.

Contrary to advice from their scientific advisors, the contacts of a person with Covid-19 are only notified when a positive test result is returned

Dr David Bonsall, from the University of Oxford’s Nuffield Department of Medicine and a scientific advisor to the NHSX app programme, said that speed is essential.

“Even with a delay of 48 hours we predict that there is about a 50pc increase in the number of infections,” said Dr Bonsall, who is also a clinician at Oxford’s John Radcliffe Hospital .

He told the Telegraph that if, from the moment someone displays symptoms, “you wait 48 hours to get your test results in before you trace that individual’s contacts there is quite a high probability that they are likely to have infected someone else.

“There is absolutely no point in contact tracing if you are not going to catch people before they have infected others.”

His colleague at the Oxford Big Data Institute, Professor Christophe Fraser said that if contacts had not been traced in six days after the initial case shows symptoms “you’ve allowed all the transmission to happen”.

Modelling by a number of institutions has shown that on average people infected with coronavirus take between five and six days to show symptoms and they are infectious for around two days before that.

Half of transmissions are said to occur before symptoms start, Dr Bonsall said, which is why it is essential to isolate infected people before they feel ill.

Scientists have repeatedly stressed that tracing needs to take place alongside other measures such as social distancing in order to keep the R number below 1.

A study by the Data Evaluation and Learning for Viral Epidemics (DELVE) group, which has been set up by the Royal Society, found that “speed is of the essence” and contact tracing alongside other measures “reduces the number of new infections otherwise occurring by 5-15pc”.

The study, which was considered by SAGE, notes that to achieve the upper end of the reduction, the contact tracing needs to be reduced to three days.

They authors say: “Our simulation model finds that reducing the overall turnaround time from five days to three leads to 60% greater reduction in R due to contact tracing of extra-household contacts”.

Meanwhile Professor Anthony Costello, who formerly ran the WHO child health programme, called on The Government to make use of the existing primary care network in England to improve test and trace.

“They've had three months and it clearly isn't working well and I'm not convinced it's going to work,” he told Today on Radio 4.

“What I don't understand is that we have 1,300 primary care networks in England, for example, of GP surgery hubs, one for every 30,000 population.

“Why can't we set up testing hubs there, with infection control nurses, courier the tests the same as you do for all your other ones, get them back the same day, have contact tracers linked to that system.”

In countries which have successfully used contact tracing to control the epidemic the testing turnaround has been short, the authors add, with it taking around five hours from swab to result in Vietnam and four in Taiwan.

Dr Guy Harling, an epidemiologist at the Institute for Global Health at University College London, who worked on the study said: “There is no one speed which fixes everything but every little bit along the way will help and every day that you get faster is better.

"Every two days you lose people, you lose infections, and the faster you can do this the fewer infections you will miss and the faster you will bring the disease under control.”

Boris Johnson told the Commons this week that currently 90pc of tests are turned around within 48 hours. He said that the majority of tests at mobile and drive through testing centres are completed within 24 hours.

The Prime Minister committed “to get all tests turned around in 24 hours by the end of June, except for difficulties with postal tests or insuperable problems like that”.

Baroness Dido Harding, who is leading the test and trace system, has promised that a weekly dashboard of data will be available soon.

She told MPs she was unable to release the number of tests which have been completed within 24 hours as the data has not been approved by the UK Statistics Authority, which has reprimanded the Government for releasing misleading testing figures.

Officials insisted that the target of 200,000 tests was not always reached on a daily basis and some of the tests were not being used specifically for contact tracing.

Of the 220,057 tests carried out on June 3, the latest figures available, 39,735 were for those in hospitals and health care workers, 136,584 were for people showing symptoms, 40,385 were for antibodies and 3,353 were part of national studies.

The number of tests does not equate to the number of people tested as some are swabbed more than once.

The system is also vulnerable to delays if people do not immediately request or take a test.

In minutes released from SAGE meetings the advisory group said that they had “high confidence” that isolation of contacts within 48 hours of a person displaying symptoms - known as an index case - was desirable.

“Modelling suggests that any delay beyond 48-72 hours of isolation of contacts, results in a significant impact on R. The sooner it is done the better,” the group concluded on the 1 May.

The minutes note that isolating of contacts should be done as soon as an index case develops symptoms, and they could then be released if that person tests negative.

“The aim should be to develop the capacity to test index cases in less than 24 hours. When this is possible, contact could be requested to isolate only when the index case tests positive,” SAGE said.

A Department of Health and Social Care spokesperson said: “The speed at which we have delivered mass testing for the public is unprecedented and is helping curb the spread of the virus and save lives.

“We have already made huge improvements in turnaround times with the majority of people who get in person tests receiving their results in less than 24 hours.

“This will further improve in the coming weeks.”