‘Very, very low detection rate’ of mass rapid lateral flow testing of university students

Professor Jon Deeks on what happens when a test is used for a purpose for which it wasn’t designed

Transcript of Radio 4 Today interview on 22 December 2020.

Radio 4 Today presenter Justin Webb: It is 7 minutes to 7. We’re promised Covid tests in schools in the new year — lateral flow tests available very cheaply and simply and easily across the board. That is why the government wants quite a few children to go back later than normal to get that system up and running. But there are concerns about the quality of those tests. We’ve heard them on the programme before, and those concerns appear to be intensifying after further work — further work in particular from Professor Jon Deeks from the University of Birmingham’s Institute for Applied Health Science. And he is on the line. Good morning to you again, professor. Hello, professor can you hear me?

Professor Jon Deeks: Good morning.

Radio 4: Tell us about the work that you’ve done, because you have told us in the past about your fears about these tests. You’ve done some further work, have you, on what has happened at Birmingham?

Deeks: Yes, the work has been led by Professor Alan McNally at the University. When we did the testing of our students at the beginning of December, we took the opportunity to re-test a large sample of the students with the gold standard PCR test. Our student testing: we tested 7,185 students came forward for testing. And we only found two positives out of all of those students, which was concerning. It was the same at other universities. They found very, very low numbers. So one interpretation of that was actually the students don’t have very much Covid. But we then went and re-tested 10% of the negatives with the PCR test, and we found another six who had Covid. So we estimate — because that was only 10% of the students — that there were probably 60 students we missed. So our summary was that we probably found two students and missed 60, with this test, because of its poor performance.

Radio 4: So if we used it for schools what would happen?

Deeks: Well, we’ll be allowing teachers and students to stay in school who had Covid. We’ll be missing people who’ve got Covid. The worst thing is actually the proposal that students — when they are in a class where one child has had Covid — they stay in the school and are tested with this test until they go positive, because inevitably there will be students left in that class who would become infectious and infect others. So we will end up with outbreaks in the school which wouldn’t happen with our current policy of sending kids home. I’ve got three kids myself. I want them to be at school. But I don’t want them to be getting Covid at school.

Radio 4: Yes, so on the basis of that, and on the basis of the work you done, are you clearly saying then that these tests will not work and should not be used in schools in January?

Deeks: Look. We used them in university without evaluating them first. That was not a good decision. We’ve evaluated them as they were being used and found it was performing poorly. Anything like this where we’re taking a new, unknown test, which has very little data as to how it works anywhere, it must be evaluated in its intended use setting before it’s rolled out across the country. It’s been different in the university — we’ve got a very, very low detection rate. It really surprised us as to how bad it is. It might possibly be better in schools. But the data are emerging that this test isn’t working well anywhere in asymptomatic people — in people who don’t have symptoms. It’s been designed to be used in people who do have symptoms. That’s what the manufacturer said it should be used [for]. So in Liverpool we await the final results of the Liverpool validations, which will be out very well [sic]. They were saying a few weeks ago that they could only detect half of the cases. We wait to see whether it’s actually got any better or any worse from that. But there’s big concern about it.

Radio 4: That is the point isn’t it, that actually what politicians are doing is using the test for something it’s not really designed to be used for?

Deeks: Absolutely. And it goes against advice from the World Health Organisation. It goes against advice from the Royal College of Pathologists, and all sorts of other groups, that are saying this test has such a high error rate. It’s an imperfect test, and when you have an imperfect test, you have to use it so carefully to make sure you don’t mislead people. And there’s a big risk this test is going to give a lot of false reassurance, which inevitably will lead to more Covid disease.

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Professor, Dept. of Philosophy, Logic & Scientific Method, LSE

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