select search filters
briefings
roundups & rapid reactions
factsheets & briefing notes
before the headlines
Fiona fox's blog

expert reaction to government announcement that asymptomatic testing is to be rolled out across country starting next week

The government have announced today that community testing offer is to be expanded across all local authorities in England to test people without symptoms.

 

Prof Iain Buchan, Executive Dean and Chair in Public Health and Clinical Informatics, Institute of Population Health, University of Liverpool, said:

“Since publication of this report, there has been a surge in demand for asymptomatic testing in Liverpool, with 74,126 residents tested between 23 December 2020 and 8 January 2021, including 19,847 in the first five days of lockdown. The low uptake of testing by young adults we reported previously changed over the holidays, with those aged 18-29 having similar uptake of testing to those aged 30-59. Those living in the most disadvantaged areas remained the most infrequent users.”

“There was a sharp rise in lateral flow and PCR test positivity over Christmas, as expected from national mixing at a time of steeply rising transmission, including the more infectious new variant. The Innova lateral flow device detects the new variant and we expect its overall sensitivity to have risen with background prevalence and viral loads.”

“The main secondary care hospital for Liverpool was at 20% Covid bed occupancy on 8 January 2021, when neighbouring were experiencing greater pressures. Further analysis is under way to estimate the possible impacts on case and hospitalisation rates from identifying over three thousand asymptomatic infections among Liverpool residents through November and December 2020.”

“As all areas face grave pressures over the coming weeks there is an opportunity to target the lateral flow test capacity at twice weekly testing for those who have to go out to work. This needs to be accompanied by adequate support for those who cannot work if they are isolating. Supermarkets and other high mixing workplaces might usefully be prioritised for staff testing, where posters may also signal a useful rhythm of testing to other workers as they shop.”

“Co-targeted testing and vaccination will be needed over the coming weeks and months, addressing vulnerability and transmission in a joined-up way. This will require locally authentic communications, timely data and intelligence, and close teamworking across NHS, local authority and academic organisations. These key components are described in the interim report. As the acute NHS pressures of the pandemic give way to deep economic challenges, more than ever, locally-grounded approaches will be needed.”

 

Professor Jose Vazquez-Boland, Chair of Infectious Diseases, Edinburgh Medical School (Biomedical Sciences), University of Edinburgh, said:

“This is most welcome and long overdue. For reasons that are difficult to understand, mass, systematic, regular screening of the population has not been considered so far a critical priority whilst it actually is the only workable strategy to control the spread of this highly transmissible virus, even if mass vaccination is implemented.  

“Perhaps because health care, rather than public health, oriented, Test & Trace has until now largely focused on testing people showing symptoms. This has been short-sighted as a strategy because it ignores the very basic fact –well-documented from the beginning of the pandemic– that asymptomatics (which can reach staggering numbers, 1 in 30 people infected as currently estimated for London) are the main source of community transmission. 

“Put in simple words, Test & Trace has been addressing the tip of the iceberg rather than tackling the much wider submerged base of asymptomatic carriers responsible for the silent spread of the coronavirus. 

“The emphasis on testing suspected cases rather than on population-wide screening has led to the necessity to repeatedly impose socially and economically highly damaging last-resort restriction measures and lockdowns, with no long-lasting effects. Relying on these is again short sighted because it is obvious that the incidence of new infections is going to rapidly rise again every time restriction measures, circuit-breakers, etc. are lifted if this highly transmissible coronavirus remains in circulation.  

“We must be clear that the only way to control the coronavirus and attempt its eradication is to immediately identify asymptomatics, as close as possible to “real-time”, to rapidly isolate them and progressively reduce the prevalence and spread of the virus across the population.  

“As obvious as this may seem, no such mass testing programme was deployed after the first wave when infection numbers dropped dramatically as a result of the strict lockdown that was then imposed. At that point, a nation-wide programme of mass screening of all the population for asymptomatic carriers would have allowed the rapid identification and targeted control of new infection outbreaks, and eventually prevented the rapid, widespread resurgence of community transmission we are continually experiencing.  A unique opportunity had therefore been lost back then after the first lockdown.  

“Learning from these lessons is critical. Mass regular SARS-CoV-2 screening must be rolled out without further delay, across the whole UK in a coordinated effort, to focus interventions only on asymptomatic transmitters and avoid the ill effects of indiscriminate restriction measures in society and the economy. 

“A coordinated systematic regular testing programme is more critical than ever now that mass vaccination is being rolled out, as mass screening is an essential tool to determine the efficacy of the vaccines in curbing the spread of the coronavirus.” 

 

Dr Angela Raffle, Consultant in Public Health and Honorary Senior Lecturer University of Bristol Medical School; Population Health Sciences, said:

“The news of further rollout of lateral flow testing is very worrying. Any benefit from finding symptomless cases will be outweighed by the many more infectious cases that are missed by these tests. Already outbreaks are known to have occurred because people have been falsely reassured by a negative lateral flow result, leading them to attend work whilst having symptoms.  The test manufacturers only recommend the Innova lateral flow test for use by qualified medical practitioners and in people with symptoms, yet the Department of Health and Social Care is pushing ahead with use in symptomless people, with the test performed by untrained staff or as a self test. This makes an important difference to the reliability. We know from testing at Birmingham University that the test may pick up as few as 2 in every 100 cases that would be positive on PCR testing, and in Liverpool it picked up no more than 40 out of every 100. For the Government to claim that these tests are accurate, reliable and ‘hugely successful’ is dangerously misleading. It could undermine the already struggling test and trace system, because people are likely to choose to get a lateral flow test rather than attending for PCR when they have symptoms.”

 

Dr James A Gill, Warwick Medical School, Locum GP for Titanium Health, said:

“Throughout the COVID-19 pandemic the issue of asymptomatic, and presumed infectious individuals has been a huge problem. How do you identify someone who feels well and has no reason, such as working in a clinical setting or care home, to organise for a COVID PCR test?

“As we approach the 1 year mark for the start of the pandemic reaching the UK, it is not unreasonable to ask of the government; what are the reasons it has taken so long for testing to be available at the scale to offer asymptomatic individuals a test?

“In general practice we have, at times, struggled to access COVID-19 tests for patients who didn’t meet the clinical guidelines for a test, yet for whom we still had a desire to exclude COVID-19. Clinically the broadening of testing availability will be a great benefit to patients and those charged with their care. 

“Regardless of delays in arriving at this point, the provision of access to rapid testing for asymptomatic individuals, in conjunction with further roll out of national vaccination strategies, may be seen as a watershed point from which society may start the long journey of returning to normality. 

“As COVID-19 cases and deaths continue to rise, looking towards a return to normality may seem premature, especially as we do not have strong estimation on the number of infections that can be attributed to asymptomatic spread. Early in the pandemic, the figure was thought as high as 80%, but now that has been drastically lowered with 20% of cases now thought to result from contact with asymptomatic individuals (1).

“Whilst asymptomatic COVID-19 positive individuals are thought to be infectious for a shorter period of time – Which may make a degree of sense if we consider that they are not going to be actively projecting virus via coughing etc – Identifying, and isolating such individuals will be a turning point, as we can hope, and expect, their identification to reduce new case trajectories by similarly large numbers (2).

“Asymptomatic individuals have so far been the wild card that we have been unable to mitigate directly, but the wider roll out of COVID-19 testing for individuals without symptomatic indication may change that. 

“National lockdowns have aimed to reduce COVID-19 spread in the general population, yet for various reasons, it has not be possible to prevent infections resulting from asymptomatic workers who have been unable to work from home, and as a result of lack of symptoms, have not been identified. Yes track and trace would theoretically have helped identify some of those sources, but for the already acknowledged flaws in that system. 

“We should welcome all additional routes to access testing for potentially COVID-19 positive individuals, as it returns to the advice from WHO last summer. The solution to COVID-19 is “testing, testing, testing””.

(1) Egli-Gany  D, Counotte  MJ, et al Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: a living systematic review and meta-analysis. PLoS Med2020;17:e1003346.doi:10.1371/journal.pmed.1003346 pmid:32960881)

(2)  Walsh  KA, Jordan  K, Clyne  B, et al. SARS-CoV-2 detection, viral load and infectivity over the course of an infection. J Infect2020;81:357-71.

 

Dr Tom Wingfield, Senior Clinical Lecturer and Honorary Consultant Physician, Liverpool School of Tropical Medicine, said:

The current Covid-19 wave threatens to overwhelm the NHS in many parts of the country. We urgently need to cut community chains of Covid-19 transmission, including in high-risk and vulnerable groups. The effects of the national lockdown on reducing Covid-19 transmission are unlikely to be seen for some weeks. Indeed, with the advent of the new variant in the UK, there are concerns that the reduction in cases may be slower than during the first lockdown in March 2020.

“Lateral flow tests are intended to rapidly identify Covid-19 cases, including in people without symptoms. The government states that its strategy to expand mass testing throughout the country is an attempt to promptly diagnose people with Covid-19 in order to break chains of Covid-19 transmission. 

“Here in Liverpool, such mass testing appeared to be acceptable and had reasonable uptake: 25% of the population were tested and 900 Covid-19 cases identified. However, an interim report of the findings of the Liverpool mass testing strategy showed that tests missed 60% of Covid-19 cases and suggested that there was no clear evidence that the strategy independently led to a reduction of cases and hospitalisations locally.1 

“Clearly, breaking chains of Covid-19 transmission is vital to relieve the strain on the NHS and reduce cases, hospitalisations, and deaths. However, it is unclear whether mass testing, the effectiveness and cost-effectiveness of which remain to be seen – is the optimal strategy to achieve this. The government’s proposed mass testing strategy appears to have been implemented without much in the way of public consultation to discuss its potential benefits and pitfalls. This is especially pertinent given the vast public expense that rolling out mass testing across the country will entail, even with some support from private enterprise.

“Questions will inevitably arise as to whether the government budget allocated for mass testing would be better spent in other areas including, for example, tackling inequalities, addressing the social and economic impact of Covid-19, and investing in the short- and long-term infrastructure of health and social care in our country.”

https://www.liverpool.ac.uk/media/livacuk/coronavirus/Liverpool,Community,Testing,Pilot,Interim,Evaluation.pdf

 

Prof Jon Deeks, Professor of Biostatistics and head of the Biostatistics, Evidence Synthesis and Test Evaluation Research Group, University of Birmingham, said:

“The Government’s plans to roll out mass testing using the Innova lateral flow test brings a real risk that it will increase rather than decrease the spread of Covid.    The Government only appears to focus on benefits of testing – that of detecting previously undetected asymptomatic cases – and not the harms which are caused by misinforming people that they do not have Covid-19 infection when in fact they do.   In Liverpool 60% of people who had the virus got a negative result from the Innova lateral flow test, and most important nearly a third of those who had high viral levels and are at very high risk of infecting others were wrongly told they were infection free.   In Liverpool the test was done by trained staff – it is unclear who will do the tests in the community, but it is known that the ability of the test to detect Covid relates to the experience of the person using it.

“Test results lead people to change their behaviour.  When you get a test result stating that you are free of disease people naturally feel safe and relax.   With the Innova test this is false reassurance – there are reports that false negatives have led people to ignore symptoms leading to disease spread, and to less strictly adhere to behaviours which prevent disease spread.  Alongside this, the Government is misleadingly overstated the accuracy of the test, wrongly telling schools and parents that “they [Innova tests] were shown to be as accurate in identifying a case as a PCR test”, and “these tests are very accurate”.   The combination of such high numbers of false negatives with such wrong information will lead to tragic consequences. Innova is unfit for purpose.”

 

Dr Alexander Edwards, Associate Professor in Biomedical Technology, Reading School of Pharmacy, University of Reading, said:

“Testing is still one of the most vital tools to combat COVID-19 – and making testing as easy to access as possible may help – but unfortunately the tests available still aren’t perfect, and limitations of all testing methods are now well known. Mass community asymptomatic testing is therefore both an opportunity to reduce spread, but will raise concerns amongst many about how it can be safe and effective, given the current weaknesses of rapid lateral flow COVID-19 antigen tests for asymptomatic testing.

“We really need to be able to spot people fast, as soon as they become infectious- but there aren’t any ideal tools to achieve this.

“One reason COVID-19 spreads so effectively is that people are often infectious and spreading virus before they experience symptoms. By the time you identify someone as COVID-19 positive through symptomatic testing, they may have spread it and it may be too late for contact tracing to contain further spread. We must identify people as early as possible- ideally as soon as they are infectious and spreading virus.

“However, almost all COVID-19 tests are designed, checked, and approved for symptomatic testing. Manufacturers typically prove their products work by testing samples from symptomatic infected patients. The accuracy drops significantly when used with larger groups of asymptomatic people. Accuracy also often drops when used in the community, rather than performed by trained experts in diagnostic labs. It’s not clear how community testing centres can even check how accurate their testing service is.

“A lot of medical experts are worried about the safety of using low sensitivity lateral flow tests (e.g. BMJ ref 1)- but they may be the only option, and in spite of their significant limitations they are relatively portable, fast, and can be mass-produced inexpensively.

“The falling sensitivity seen in different studies powerfully illustrates limitations of asymptomatic lateral flow testing. The manufacturer states very high accuracy (over 95%)- almost as good as lab PCR. The PHE laboratory evaluation suggests lower sensitivity in a lab (e.g. 70%) and even lower in the community (2).  The Liverpool public health pilot suggests less than half positive cases are detected, with sensitivity falling below 50% (3). These accuracy figures are compared with PCR- yet PCR is not perfect and can’t pick up all infected cases.

“Because some studies show that fewer than half infected people will be detected, it’s clear that a negative lateral flow result does NOT mean someone is not infected and “safe”. This mass asymptomatic testing is not supposed to help people check if they are ‘safe’. Instead it aims to pick up more cases to support contact tracing and isolation of people at high risk of transmitting the virus before they know they are infected. People must be told clearly that a negative test does not rule out being infected.

“These lateral flow tests do appear to be very specific- they very rarely give false positives- so anyone testing positive is extremely likely to have COVID-19 and must isolate, although confirmation by PCR may be advised and remains best practice.

“At the moment, the national “stay at home” orders should minimise contacts and thereby reduce infection levels. But we must still strive to use all means possible to identify infected people, trace their contacts, and support isolation. Careful use of lateral flow testing in the community, if combined with essential coordinated public health measures, could help, assuming the known performance limitations can be overcome.”

1 https://www.bmj.com/content/371/bmj.m4848

2 https://www.ox.ac.uk/sites/files/oxford/media_wysiwyg/UK%20evaluation_PHE%20Porton%20Down%20%20University%20of%20Oxford_final.pdf

3 https://www.gov.uk/government/publications/innova-lateral-flow-sars-cov-2-antigen-test-accuracy-in-liverpool-pilot-preliminary-data-26-november-2020

 

Prof Adam Finn, Professor of Paediatrics at the University of Bristol, said:

“The widespread deployment of rapid tests to be used by people who do have no symptoms of COVID but who may be in contact with others is a vitally important additional measure to those already in place aiming to reduce transmission of this virus in our community. These are “red light“ tests. If they come positive that means you are potentially infectious to others and must self isolate. They are not “green light” tests. You cannot be sure that if the test is negative you are not infectious and you must continue to take the usual precautions. Added to the measures already in place, this provides an important new tool to help to reduce the rapid rise in cases that is paralysing in our country. Even though the vaccine programme is now ramping up it will be some time before it has a major impact on the number of hospitalisations and deaths. Using these tests wisely and widely is a powerful way to enable people to play their part in fighting the present crisis in the pandemic.”

 

Prof Sheila Bird, formerly Programme Leader, MRC Biostatistics Unit, CAMBRIDGE, said:

“Testing plus evaluation is required. Messaging should not mislead.

“There is merit in key workers having access to regular testing for SARS-Cov-2: either prioritized pooled RT-PCR testing (eg at the start and end of each working-week for a group of 8-10 key workers, with individual re-testing if the pool is positive, as offered to students by the University of Cambridge) or on-site individualized lateral flow testing with honest messaging about the implication of low sensitivity and, as necessary, evaluation to double-check the LFT’s  in-context sensitivity or at-home individualized lateral flow testing –  if approved by the Medicines and Healthcare products Regulatory Agency.

“Uptake of repeated testing needs to be monitored and practical support given for key workers who test positive and are required to self-isolate. Their self-isolation should itself include random testing to glean intelligence on whether the period of self-isolation can be reduced, or needs to lengthen – dependent on whether the key worker was (or was not) infected by the Variant of Concern. Early RT-PCR testing of other self-isolating members of an infected key worker’s household, and repeat testing after (say) 7 days, would allow more efficient learning about within-household transmission than Test & Trace (without follow-up testing) has delivered thus far.

“Messaging should not mislead. Consider, for example, the over-statement: “Targeted, regular community testing using lateral flow tests is highly effective and has already identified over 14,800 positive Covid-19 cases who would not have been identified without targeted asymptomatic testing, breaking chains of transmission in the community.”

1. Lateral flow test (LFT) sensitivity was 40% (95% CI: 29% to 52%) when Liverpool evaluated INNOVA lateral flow testing for around 5,900 asymptomatic citizens: that is, 2 detected positives by LFT versus 5 by RT-PCR (28/70, see https://www.liverpool.ac.uk/media/livacuk/coronavirus/Liverpool,Community,Testing,Pilot,Interim,Evaluation.pdf).

2. Liverpool evaluation did not report what percentage of asymptomatic citizens who attended for an initial screening test returned for a second screening within a week of the first. Messaging is important: LFT negative does not guarantee uninfected.

3. How many asymptomatic persons detected by LFT remained asymptomatic for the next 10 days? (Those who were pre-symptomatic at LFT would have developed symptoms in a few days: over-statement here is unnecessary  – due to the benefit from time-saved in advancing the start of self-isolation even for pre-symptomatic LFT-positives –  and misleading).

4. Follow-up of the 14,800 LFT-positives should have told us: a) how many remained asymptomatic after 10 days; b) for those who developed symptoms within 10 days, what was their waiting-time from LFT-date to symptom-onset-date? If known, please report. If unknown, please organize to evaluate for key workers.

5. The Liverpool evaluation team may be well-placed to provide answers to question 4 for their nearly 900 LFT positives in November/early December 2020.”

 

Dr Shaun Fitzgerald Director, Centre for Climate Repair at Cambridge, said

“This initiative is very welcome. The regular testing of students last term (Oct-Dec 2020) across Cambridge University really helped identify new cases. The resulting immediate isolation of households then enabled the transmission to be seriously suppressed. Early detection of emerging cases can have a significant impact so having this rolled out country-wide is a positive step.”

 

Professor Lawrence Young, Virologist and Professor of Molecular Oncology, Warwick Medical School, said:

“This is good news. We are currently in the eye of a perfect storm with a more infectious virus fuelling increased infections across the country, cold weather (which the virus likes) and a lockdown that is too lax. Asymptomatic testing of individuals who are unable to stay at home during the current lockdown will help to restrict the spread of infection as long as we ensure that folk who test positive appropriately isolate and that their contacts are traced and also isolate. Repeat testing is essential given the nature and time course of virus infection and concerns about the accuracy of lateral flow tests. Standard measures to restrict transmission (hands, face, space) will prevent infection with the UK and other virus variants. Along with improved surveillance (testing, tracing and isolating) and expediating the roll out of vaccines, these measures will prevent virus transmission, alleviate the pressure on the NHS and allow us all to look forward to the return of normal life.”

 

Simon Clarke, Associate Professor in Cellular Microbiology, Head of Division of Biomedical Sciences & Biomedical Engineering, said:

“There has been a lot of debate surrounding the accuracy of lateral flow tests.  The government claims that its scientists have identified kits with 70% sensitivity, but which detect everyone with a high viral load and who are therefore likely to be the most infectious. 

“Increased testing in the wider population has the potential to suppress viral transmission, if done it’s right.  It is often claimed that they worked to drive down infections in Liverpool, which is highly questionable. 

“This sort of testing will need to be supervised, as efficacy drops in untrained hands and if someone is allowed to conduct their own testing, they’ll need to be incentivised to comply with the self-isolation following a positive result.  Someone who would be disadvantaged by a positive test result, say due to loss of income or loss of something they’ve paid for like a ticket to a football match or the theatre, might feel too much temptation to cheat the test or not report a positive result.”

 

 

Declared interests

None received.

in this section

filter RoundUps by year

search by tag