{"id":49624,"date":"2021-02-19T15:22:06","date_gmt":"2021-02-19T14:22:06","guid":{"rendered":"https:\/\/blogs.bmj.com\/bmj\/?p=49624"},"modified":"2021-03-22T11:00:35","modified_gmt":"2021-03-22T10:00:35","slug":"testing-asymptomatic-individuals-for-sars-cov-2-known-unknowns","status":"publish","type":"post","link":"https:\/\/blogs.bmj.com\/bmj\/2021\/02\/19\/testing-asymptomatic-individuals-for-sars-cov-2-known-unknowns\/","title":{"rendered":"Testing asymptomatic individuals for SARS-CoV-2\u2014known unknowns"},"content":{"rendered":"<p><i><span style=\"font-weight: 400\">On 11 February 2021, <\/span><\/i><em><span style=\"font-weight: 400\">The BMJ<\/span><\/em><i><span style=\"font-weight: 400\"> hosted a webinar on testing asymptomatic individuals for SARS-CoV-2. An expert panel discussed the role of asymptomatic transmission, as well as testing in a pandemic, and how to communicate and act on test results. Nikki Nabavi and Juliet Dobson report<\/span><\/i><\/p>\n<p><span style=\"font-weight: 400\">The theme of the webinar was inspired by an editorial published in <\/span><i><span style=\"font-weight: 400\">The BMJ<\/span><\/i><span style=\"font-weight: 400\"> called \u201c<\/span><a href=\"https:\/\/www.bmj.com\/content\/371\/bmj.m3979\"><span style=\"font-weight: 400\">Covid-19\u2019s known unknowns<\/span><\/a><span style=\"font-weight: 400\">.\u201d The key message: \u201cThe more certain someone is about covid-19, the less you should trust them.\u201d <strong><a href=\"https:\/\/www.bmj.com\/covid-19-webinars\">Register for future events here<\/a>.\u00a0<\/strong><\/span><\/p>\n<p><iframe loading=\"lazy\" title=\"Testing for SARS-CoV-2 in asymptomatic people (part of the #CovidUnknowns series)\" width=\"640\" height=\"360\" src=\"https:\/\/www.youtube.com\/embed\/L9Bq4sOnfQE?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><\/p>\n<p>&nbsp;<\/p>\n<p><b>Role of testing in a pandemic\u00a0<\/b><\/p>\n<p><span style=\"font-weight: 400\">Muir Gray reminded us of the opening lines from his <\/span><a href=\"https:\/\/www.ncbi.nlm.nih.gov\/pmc\/articles\/PMC2258553\/\"><span style=\"font-weight: 400\">book<\/span><\/a><span style=\"font-weight: 400\">: \u201cAll screening programmes do harm; some do good as well, and, of these, some do more good than harm at reasonable cost.\u201d\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">When asked by the audience whether they viewed testing asymptomatic individuals for SARS-CoV-2 as screening or case finding, Sian Taylor-Philips said: \u201cTo me, it&#8217;s definitely screening. You&#8217;re inviting people without symptoms, who don&#8217;t think they&#8217;ve got the disease, for a test to see if they have got it. The way it differs from the screening we are used to is that a lot of the benefit is not for the person who came for the test, but for transmission to others. Though all of the principles of screening apply in exactly the same way.\u201d<\/span><\/p>\n<p><span style=\"font-weight: 400\">Angela Raffle didn\u2019t think that labels mattered as long as a programme is well designed. She shared some principles with the audience that helped frame the rest of the conversation on mass testing. The focus should be first on high risk groups for transmission (people with symptoms and their contacts)\u2014\u201cWe want to find people who will transmit\u201d the virus. For treatment, we look at the evidence before we make a policy decision, and the same must apply for testing programmes. The importance of a uniform national reference standard for what is defined as \u201ca case,\u201d which \u201cwe still don\u2019t have.\u201d\u00a0\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u201cPart of the problem is that there have been two parallel conversations going on\u201d added Brian McCloskey, \u201cSome people are raising questions about the risks of testing for negatives, and others about the benefits of testing for asymptomatic positives&#8230;testing for positives and testing for negatives are fundamentally different concepts, and they require different approaches.\u201d<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u201cYou can\u2019t design a valuable system unless you\u2019re really clear what you\u2019re wanting to <\/span><span style=\"font-weight: 400\">achieve\u201d said Raffle. \u201cIf we want to control the pandemic the primary concern must be health outcomes, not photo opportunities for politicians, not profits for shareholders, not research empires.\u201d\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">Asymptomatic individuals often share the same motivation for wanting a test<\/span><span style=\"font-weight: 400\">\u2014<\/span><span style=\"font-weight: 400\">\u201cthey want to be told that they\u2019re okay,\u201d said Raffle. \u201cThe humans in the system behave in many ways, and how we give them clear, clean information is crucially important.\u201d<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u201cWe are trying to detect infectious, asymptomatic people with SARS-CoV-2 and isolate them\u2014to decrease transmission.\u201d said Taylor-Philips. \u201cMass testing will stop some people from transmitting,\u201d she added, \u201cbut it could increase transmission from some other people . . . testing negative doesn&#8217;t mean you are safe.\u201d McCloskey added that \u201ctesting alone does not stop transmission. Testing followed by appropriate action does.\u201d<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u201cMaybe it&#8217;s a distraction, maybe because testing everyone is such an intuitively attractive idea, maybe for commercial reasons. The UK government is keen to take us down the route of society wide testing. This is like checking hundreds of times for a leak when we haven&#8217;t yet attended to the burst water main.\u201d Raffle added.<\/span><\/p>\n<p><b>Asymptomatic transmission<\/b><\/p>\n<p><span style=\"font-weight: 400\">How common is asymptomatic SARS-CoV-2? How infectious is it? And how much does it actually contribute to overall transmission? Nicola Low spoke on behalf of herself and Muge Cevik to outline the role of asymptomatic transmission. She cited a <\/span><a href=\"https:\/\/www.bmj.com\/content\/369\/bmj.m1375\"><span style=\"font-weight: 400\">BMJ news piece<\/span><\/a><span style=\"font-weight: 400\">, which has been used to imply that the death rate from covid might be lower than we think that it is, because undetected people have somehow been left out of the denominator, and explained that these claims are untrue. One difficulty when identifying our picture of who is asymptomatic is the fact that everyone who tests positive is initially presymptomatic (i.e. asymptomatic until they subsequently develop symptoms):\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u201cAt a single point of time, you can&#8217;t distinguish between someone who is presymptomatic and someone who is going to remain asymptomatic, so that means if you have a cross sectional study that at a single point in time says four fifths of people are asymptomatic as this news item in <\/span><i><span style=\"font-weight: 400\">The BMJ<\/span><\/i><span style=\"font-weight: 400\"> did, that does not mean that four fifths of people are truly asymptomatic.\u201d She added that the definition of \u201casymptomatic\u201d is also challenged by the fact that the spectrum of symptoms we identify keep changing\u2014in January 2020 we were aware of respiratory symptoms, but by March 2020 we were aware of a broader spectrum of signs and symptoms, including anosmia.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u201cTypes of evidence have changed over time,\u201d concluded Low, \u201cdefinitions have changed over time. Types of studies have changed over time. We can&#8217;t use cross sectional studies to assess the proportion of asymptomatic, and serological studies are difficult to interpret . . . [but] context is everything.\u201d<\/span><\/p>\n<p><b>Asymptomatic testing: are the tools fit for the job?<\/b><\/p>\n<p><span style=\"font-weight: 400\">Can we identify people who are infectious or not? Jon Deeks spoke about the <\/span><span style=\"font-weight: 400\">evidence on the relation of lateral flow tests and infectiousness<\/span><span style=\"font-weight: 400\">\u2014<\/span><span style=\"font-weight: 400\">a key part of the arguments for testing asymptomatic individuals. He presented a rapid run through of existing evidence and concluded, \u201cwe can&#8217;t really be talking about tests of infectiousness. And we should be looking at stopping this language because I think it&#8217;s giving the wrong message. We really urgently need to find better tests&#8230;It&#8217;s really important to get sensitive lateral flow tests. They will be the future for us, but not the ones that we&#8217;ve got now.\u201d\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">Tim Peto highlighted the challenge of making decisions in a pandemic: \u201cYou have no time to get the right evidence. So you&#8217;ve got to go on the evidence of the balance of probability. You can&#8217;t be purist about this because people have to make decisions now about what to do for the best.<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u201cW<\/span><span style=\"font-weight: 400\">e are trying to quarantine people we believe are infectious, and we&#8217;re doing this without much evidence. So the evidence for social distancing, face masks, all that stuff is all in the balance of probability,\u201d he said.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">Patrick Bossuyt picked up on a point that Phil Hammond made at the start of the webinar when Hammond said that we don&#8217;t have tests for infectiousness. \u201cThat&#8217;s not entirely true&#8230;we have a range of things to use for SARS-CoV-2. The only thing is we don&#8217;t know how good they are for evaluating infectiousness because we lack a clinical reference standard&#8230;That is the most known unknown in this whole discussion about whether we have the right tools. I think we have a range of tools. The question is, we don&#8217;t know yet how good they are, and that makes decision making difficult.\u201d<\/span><\/p>\n<p><b>Communicating and acting on test results<\/b><\/p>\n<p><span style=\"font-weight: 400\">Theresa Marteau discussed the <\/span><span style=\"font-weight: 400\">behavioural responses to a negative test and asked whether we should be worried about the potential for false reassurance after negative results, which is one of the many sets of behaviours that are key to mass asymptomatic testing. <\/span><span style=\"font-weight: 400\">\u201cA <\/span><span style=\"font-weight: 400\">negative result does decrease behaviours that reduce transmission, she said. \u201cBut, importantly, we don&#8217;t know the precise nature or the scale of that,\u201d as currently the evidence to draw on is limited.<\/span><\/p>\n<p><span style=\"font-weight: 400\">Jackie Cassell spoke about the impact that the vaccination programme will have on people\u2019s behaviours. As the vaccination rollout continues, \u201cWe will see a growing concentration of all the remaining cases and transmissions in younger workers and in children and students,\u201d she said. So we can expect to see a shift in people\u2019s behaviours and their willingness to comply with testing and isolating. But we don\u2019t yet know how that will play out. So the question is: \u201cWhat changes and choices will we make about test, trace, isolate and the people on whom that burden falls and on what evidence?\u201d\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">Support for self isolation is crucial, Cassell said, \u201cClearly the scale of people feeling they cannot even test because they cannot afford to isolate, that is something that is an issue at whatever scale. And we need to think about that as that goes on for some people and not for others.\u201d<\/span><\/p>\n<p><span style=\"font-weight: 400\">Marteau underlined this point:\u201cOne of the key pieces of evidence that we&#8217;ve had is how people still do not have effective support packages. So for people to self isolate the support needs to be financial, practical, social, and clinical. And until we have that in place, we&#8217;re going to have more virus in the community.\u201d\u00a0<\/span><\/p>\n<p><b>Testing in different settings and contexts<\/b><\/p>\n<p><span style=\"font-weight: 400\">The final session focused on testing in different settings<\/span><span style=\"font-weight: 400\">\u2014<\/span><span style=\"font-weight: 400\">workplaces, prisons, and the community.<\/span><\/p>\n<p><span style=\"font-weight: 400\">Pete Buckle highlighted the impact that a loss of trust in the testing system will have, not just on testing for SARS-CoV-2 but on other public health interventions:<\/span><b> \u201c<\/b><span style=\"font-weight: 400\">We&#8217;re really quite concerned about the wider implications of a system where, let&#8217;s just be honest, the public think that it&#8217;s either a positive or a negative test\u2014you&#8217;ve either got it or you haven&#8217;t. So I think the real world implementation of these things really does need to be thought about very carefully.\u201d<\/span><\/p>\n<p><span style=\"font-weight: 400\">Andrew Frazer spoke about the challenges of testing in prisons. One of the main risks of infection is from staff as they are <\/span><span style=\"font-weight: 400\">more mobile. \u201cThat is maybe where we need to spend more time thinking about the risks and the appropriate tests,\u201d he said.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u00a0Returning to the earlier point about support packages for self isolation, he asked: \u201cWhat is the support package in prison? There are incentives and disincentives to knowing whether you&#8217;re positive or negative, but mainly drawbacks because you go from a very poor regime, and it gets even poorer if you are needing to be further isolated.\u201d<\/span><\/p>\n<p><span style=\"font-weight: 400\">The final speaker, Stefan Baral, spoke about his experience of community testing, and testing in homeless shelters. He emphasised that \u201c<\/span><span style=\"font-weight: 400\">a testing programme should integrate education and clinical services and programme management. It should be based on equity and ensure broad access to screening, and we should have an evaluation built into it.\u201d<\/span><\/p>\n<p><span style=\"font-weight: 400\">\u201cI find it unethical to offer people testing without offering them an intervention in response. I find it unethical to blame individuals for the sorts of decisions that I hope to never be in a place to have to make in terms of risking not being able to feed my family versus not going to work.\u201d<\/span><\/p>\n<p><strong>This webinar was part of <a href=\"https:\/\/www.bmj.com\/covid-19-webinars\"><em>The BMJ<\/em>&#8216;s series of covid-19 known, unknowns webinars<\/a>. Find out more and register for future events <a href=\"https:\/\/www.bmj.com\/covid-19-webinars\">here<\/a>.\u00a0<\/strong><\/p>\n<p><em><strong>Nikki Nabavi<\/strong>, editorial scholar, The BMJ<\/em><\/p>\n<p><em><strong>Juliet Dobson<\/strong>, editor bmj.com, The BMJ<\/em><\/p>\n<p><em><strong>Competing interests<\/strong>: none declared.<\/em><\/p>\n<p><span style=\"font-weight: 400\">&#8212;<\/span><\/p>\n<p><strong>Panel and Agenda<\/strong><\/p>\n<p><span style=\"font-weight: 400\">Role of testing in a pandemic\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">Chair: Muir Gray<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Angela Raffle (University of Bristol)<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Sian Taylor-Philips (University of Warwick)<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Brian McCloskey (Chatham House)<\/span><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"font-weight: 400\">Role of asymptomatic transmission?\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">Chair: George Davey Smith, Bristol University<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Nicola Low (University of Bern)<\/span><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"font-weight: 400\">Asymptomatic testing: are the tools fit for the job?\u00a0 (Covering accuracy in real world and Interpretation of results)<\/span><\/p>\n<p><span style=\"font-weight: 400\">Chair: Sheila Bird\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Jon Deeks (University of Birmingham)<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Tim Peto (University of Oxford)<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Patrick Bossuyt (University of Amsterdam)<\/span><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"font-weight: 400\">Communicating and acting on test results\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">Chair: Allyson Pollock<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Theresa Marteau (University of Cambridge) covering behavioural responses to negative tests<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Jackie Cassell (Brighton &amp; Sussex Medical School) on the effectiveness of interventions]<\/span><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"font-weight: 400\">Testing in different settings\/contexts: panel\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400\">Chair: Fiona Godlee, The BMJ<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Pete Buckle (NIHR In Vitro Diagnostics C., London) covering workplace and care home settings<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Andrew Frazer (former DCMO Scotland) covering prisons<\/span><\/p>\n<p><span style=\"font-weight: 400\">&#8211; Stefan Baral (Johns Hopkins University) covering community settings<\/span><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"font-weight: 400\">Discussion<\/span><\/p>\n<p><span style=\"font-weight: 400\">Chair: Phil Hammond<\/span><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>On 11 February 2021, The BMJ hosted a webinar on testing asymptomatic individuals for SARS-CoV-2. An expert panel discussed the role of asymptomatic transmission, as well as testing in a [&#8230;]<\/p>\n<p><a class=\"btn btn-secondary understrap-read-more-link\" href=\"https:\/\/blogs.bmj.com\/bmj\/2021\/02\/19\/testing-asymptomatic-individuals-for-sars-cov-2-known-unknowns\/\">More&#8230;<\/a><\/p>\n","protected":false},"author":66,"featured_media":49143,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[18932],"tags":[],"class_list":["post-49624","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-covid-19-known-unknowns-webinars"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Testing asymptomatic individuals for SARS-CoV-2\u2014known unknowns - The BMJ<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.bmj.com\/bmj\/2021\/02\/19\/testing-asymptomatic-individuals-for-sars-cov-2-known-unknowns\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Testing asymptomatic individuals for SARS-CoV-2\u2014known unknowns - The BMJ\" \/>\n<meta property=\"og:description\" content=\"On 11 February 2021, The BMJ hosted a webinar on testing asymptomatic individuals for SARS-CoV-2. 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