Mass Covid testing could lead to spike in transmission, experts say

Mass Covid testing scheme could lead to spike in transmission because Brits with symptoms may ditch lab tests for less accurate at-home kits, experts say

  • Dr Angela Raffle and Dr Mike Gill blasted the Government’s mass testing plan
  • They said lateral flow tests could risk spreading the virus further in the UK
  • England has rolled out millions of these to schoolchildren and adults 

Mass coronavirus testing could lead to spikes in transmission because Britons with symptoms may bypass more accurate lab tests, experts fear.

Current guidelines require everyone with tell-tale Covid signs — a high temperature, cough or loss of taste and smell — get a reliable PCR test.

But Public Health England’s Dr Angela Raffle and Dr Mike Gill say the roll-out of rapid lateral flow tests will lead to infected people opting for these less accurate swabs instead.

Writing in the British Medical Journal, they warn: ‘The temptation for people with symptoms to opt for unsupervised, rapid and lower sensitivity self-testing may lead to false reassurance, as happens with other screening, leading to potential increases in transmission.’

They added testing asymptomatic individuals — a crucial part of No10’s effort to live with the virus — was also unlikely to reduce the spread.

And they said the UK has been an ‘outlier’ globally in pursuing ramping up testing for the virus.

England rolled out millions of lateral flow kits when schools were reopened in March, and asked all pupils to test themselves for the virus twice a week. It has now opened the programme to include everyone in the country.

PCR tests are the gold-standard for Covid but take up to two days to produce results. Lateral flow tests give answers in as little as 15 minutes but are much less accurate. 

More than one million tests are being carried out in Britain each day but only around 300,000 of these were PCR swabs.

The UK’s coronavirus testing system for travellers could ‘buckle’ when foreign holidays resume, a consumer group has warned.

Which? said social media and review sites are already ‘flooded’ with complaints from people who have suffered delays in receiving their test kits and results.

That is despite passenger numbers being a fraction of normal levels due to the ban on overseas leisure travel.

The consumer group claimed the system is ‘at risk of being overwhelmed, and potentially collapsing’ when foreign holidays resume, which is expected to happen for people in England on May 17.

People arriving in England are required to quarantine, and pre-book two PCR tests from a private firm on a Government list.

The two-test package typically costs between £100 and £200, but can exceed £500.

Negative results from both tests – taken on days two and eight after arrival – must be received before someone can leave quarantine.

But travellers have reported long delays in receiving kits or results, forcing them to either pay for additional tests or extend their quarantine period beyond the initial 10-day period.

Demand for tests will soar once holidays resume.

Returning travellers will require one or two post-arrival tests depending on which country they have visited. 

Slamming mass testing for asymptomatic individuals, the experts wrote: ‘We have no empirical data to support mass Covid screening, and home self-testing has not been evaluated.

‘The December surge of infections in Liverpool, where trained testers screened a quarter of the population, was no lower than in other cities without screening. 

‘Care homes conducting asymptomatic testing have struggled to adhere to protocols and experienced no fewer outbreaks than care homes without asymptomatic testing.

‘From early March, testing of millions of schoolchildren was accompanied by a short lived rise in the ascertainment of school age cases, but there is no evidence of change in the trajectory of case rates in older age groups, suggesting a lack of effect on onward transmission.’

They added: ‘The UK is an outlier globally in placing such emphasis on asymptomatic testing. 

‘From May 2020, ministers focused their efforts on reaching targets for test numbers, creating centrally commissioned “lighthouse” laboratories and disregarding the quality of the tests or of the overall programme.

‘They also commissioned a separate initiative for evaluating rapid tests, bypassing highly effective and flexible processes and expertise both in developing screening programmes—the UK National Screening Programmes—and in evaluating diagnostic tests—for example, the med tech and in vitro diagnostics cooperatives funded by the National Institute for Health Research. 

‘The challenge was framed as “find a valid test and roll it out as quickly as possible” rather than “devise best systems for using testing to help contain the pandemic.”’

They said: ‘The issue is not, and has never been, about whether to test but about how to do it most effectively.’

A PCR test takes around 24 hours and involves multiplying a sample and then screening it for a virus genome.

On the other hand, a lateral flow test can give results in up to 30 minutes but studies suggest they are less accurate.

A scientific review found they were only 58 per cent accurate among asymptomatic individuals. But academics warned firm conclusions could not be drawn because this was based on a small sample of individuals.

The Government has spent more than £2billion on lateral flow devices, and purchased them mostly from Innova — a Californian firm set up by a Chinese-born businessman.

Around a third of all Covid cases are asymptomatic, according to official estimates. 

Responding to the editorial the Covid response director for Public Health England, Dr Susan Hopkins, said: ‘Around one in three people with Covid experience no symptoms and there is clear evidence that rapid testing detects cases quickly, meaning positive cases can isolate.

‘After building a testing system from scratch, we have now carried out over 149.2million Covid tests – more than any other country in Europe.

‘These tests have helped enable children to return to school, businesses to reopen and the latest easing of national restrictions.

‘Meanwhile, the NHS Test and Trace app has already prevented an estimated 600,000 Covid cases since its launch.

‘Protecting communities and saving lives is always our first priority and every pound spent on testing is contributing towards our efforts to keep people safe.’ 

HOW LATERAL FLOW TESTS ARE ONLY TRUSTWORTHY WHEN ADMINISTERED BY TRAINED STAFF

Lateral flow tests are only accurate at diagnosing coronavirus when administered by trained professionals, studies have repeatedly shown. 

The tests, which give results in as little as 15 minutes, use swabs of the nose or throat. Samples are then mixed in a testing liquid and put into a plastic cassette which can detect the presence or absence of coronavirus and then produce an image of a line, the same way as a pregnancy test, to indicate whether it is positive or negative.

The Department of Health and NHS are instructing people to use the tests on themselves, despite manufacturers of some kits saying they shouldn’t be used as DIY swabs.

Both the swabbing procedure and the use of the test cassette can easily be done wrong and affect the accuracy of the test. 

If the swab isn’t done for long enough, or deep enough into the nose or throat, it may not pick up fragments of virus. Medical professionals are also able to use nasopharyngeal swabs, which go right to the back of the nostril, whereas this is not advised for people who test themselves.

And if the sample isn’t properly inserted into the cassette the result might be wrong, or people may misread the display when it produces a result. 

SELF-TESTING CUT ACCURACY FROM 79% TO 58%

A University of Oxford and Public Health England evaluation of the Innova lateral flow test, which is being widely used in the UK, found its sensitivity – the proportion of positive cases it detected – fell from 79 per cent to 58 per cent when it was used by untrained members of the public instead of lab experts. 

Based on this evaluation, officials pushed ahead and used it for a real-world self-testing trial.

PILOT IN LIVERPOOL FOUND FEWER THAN HALF OF POSITIVES

When the same Innova test was trialled on members of the public in Liverpool – with people taking their own swabs and trained military staff operating the tests – the swabs picked up just 41 per cent of positive cases.

In the study the rapid tests detected 891 positive results, compared to lab-based PCR swabs that found 2,829 positives in the same group. This means 1,938 people got a wrong negative result from the rapid test.

The study didn’t compare this to professionally done rapid tests, but the manufacturer Innova claims its test is 95 per cent sensitive in lab conditions. 

…BUT TESTING DONE BY MEDICS IN SLOVAKIA ‘REDUCED INFECTIONS’ 

Despite rapid lateral flow tests getting bad press, officials in Slovakia used them on 5.2million people – almost the entire population of 5.5m – in a trial that a study later estimated to have cut the country’s infection rate by 60 per cent.

The tests used were between 70 and 90 per cent accurate and all the swabs and evaluations were carried out by trained medical workers. They used deep nasopharyngeal swabs, that go to the back of the nose, whereas self-testing generally relies on a swab of only the nostril.

London School of Hygiene & Tropical Medicine researchers said that the scheme successfully weeded out coronavirus cases that wouldn’t have been found otherwise, slashing the number of cases by over half in a week during a lockdown. 

HOW RAPID TESTS ARE DIFFERENT TO LAB-BASED PCR SWABS 

Lateral flow tests are an alternative to the gold standard PCR test – known scientifically as polymerase chain reaction testing – which is more expensive and more labour-intensive but more accurate.

PCR tests also use a swab but this is then processed using high-tech laboratory equipment to analyse the genetic sequence of the sample to see if any of it matches the genes of coronavirus.

This is a much more long-winded and expensive process, involving multiple types of trained staff, and the analysis process can take hours, with the whole process from swab to someone receiving their result taking days.

It is significantly more accurate, however. In ideal conditions the tests are almost 100 per cent accurate at spotting the virus, although this may be more like 70 per cent in the real world. 

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