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TThis week, student coronavirus tests are rolling out at UK universities. Some institutions already wrongly claim that if your test is negative, you will know that it is safe to return home. The issue is very important to many families, who do not want their children to be stranded while isolating themselves at university for Christmas, but are also concerned that they are bringing the coronavirus home to elderly or vulnerable relatives.
In my work as a professor of population health, I help national governments and legislators decide whether to run screening programs like those carried out in universities. This is what we know and what we don’t know about college exams.
A preliminary evaluation by Public Health England (PHE) found that the new lateral flow test used by universities, which delivers a result in 30 minutes, had previously missed coronavirus cases between a quarter and a half of the people tested, by giving a negative reading. It’s not simply an issue with the particular manufacturer the government chose – most rapid lateral flow-type coronavirus tests seem to miss many people with coronavirus.
Many recently infected students (a few days before the test) will also be lost: this is because the coronavirus only becomes detectable a few days after the infection has occurred. Therefore, students who test negative on two tests a few days apart, and self-isolate in between, have the least chance of having coronavirus, but because the test does not detect cases, they may still be infected. Many colleges do not advocate self-isolation between tests, so many infected students will also be lost in the time between the two tests.
The existing test and trace program should detect individuals with symptoms and their contacts. The idea behind rapid university tests is to find students who have coronavirus, but have no symptoms (probably around one in five infected people), so they can self-isolate rather than bring the infection home. For this to work, you need two things. First, to accurately detect the coronavirus in students without symptoms. The directions for use of the lateral flow test actually say it is for people with symptoms, not students without symptoms, for whom it is primarily used here. Second, for the process to work, we need students and their contacts to self-isolate themselves if coronavirus is detected. We don’t know if they will do this, but evidence from testing and tracing suggests that many people do not. So ultimately, college testing may not cut down on streaming as much as expected.
The thing about screening programs is that they often don’t deliver the expected result. There are some obvious ways that the college screening program could increase the spread of the coronavirus. The real danger is that students mistakenly believe that a negative test means they do not have coronavirus. It would be hard to blame students for such a misunderstanding when a health minister, Lord Bethell, announced that evaluations “are already showing that lateral flow testing can be the highly sensitive and reliable technology we need”, and the secretary of health, Matt Hancock said he “did not recognize” the PHE figures showing the missing test cases.
Given the limitations of this rapid test, some students will go straight home after a negative result and will be infectious immediately or become infectious in a few days. This would happen whether they had been tested or not. The problem arises if they mistakenly believe they are not infectious because they had a negative test and are visiting an elderly or vulnerable relative under that misunderstanding. There are other possible unintended consequences – some students, for example, may misinterpret a negative test result as a free pass to the party, which could also increase streaming.
There is not much evidence on whether college screening tests will do more good than harm, or if they will generally decrease or increase infections. We still don’t know how many students will take the tests and how they will react to positive or negative results, among many other things.
In a pandemic, decision-making is more urgent and there is little time to gather research evidence. However, in the UK we have fantastic researchers, dedicated funding streams and organized systems to gather this evidence very quickly. We are not launching a vaccine before finding out if it is safe and effective – we are waiting for evidence from the randomized trial. However, it seems that we are immersing ourselves in mass detection. In the field of research we have investigated many other screening programs that seem like good common sense, but when we do a randomized trial, it often turns out that they do the opposite of what was intended.
Another lesson learned from decades of successfully running screening programs in the UK is the importance of honesty. Authorities must be honest with people about the good and bad parts of screening, and allow them to make their own informed decision to participate. Families have gotten used to balancing risks this year: We should tell them openly that these tests can detect some asymptomatic cases, but they, too, miss some, and rely on people to make sensible decisions for their own families.
This approach will help avoid the worst possible outcome when screening students for the coronavirus – that young people returning home end up infecting elderly or vulnerable family members due to a misunderstanding of what negative results mean. Not only would that cause a completely avoidable tragedy for families, but people could also lose faith in the government over the next initiative: the launch of critically important vaccines.
• Dr. Sian Taylor-Phillips is professor of population health at the University of Warwick and specializes in evaluating population screening programs.
