Two-hour coronavirus test
“Test! Test! Test!” the World Health Organisation have said, counselling the world on how it should proceed in trying to gain control of the coronavirus pandemic. But scaling up to offer tests to large numbers of people, as well as making tests fast and agile, has proved difficult. Now researchers at the University of Cambridge and the company Diagnostics for the Real World, have repurposed a rapid HIV test so it can detect coronavirus infections in just ninety minutes. The system generates multiple copies of the genetic information for the virus - if it’s present - and then produces a visible pattern of three lines on a read out... as well as an electronic log of the results. Chris Smith spoke with Dami Collier who’s been working on the new system...
Dami - This is a rapid diagnostic test for COVID-19, so it's rapid in the sense that from taking the sample from the patients, which is usually a swab of the back of the throat and the nose, to the point of being able to give them test results has been cut down dramatically, from what is ordinarily between one or three days, to two hours. So it is a game changer for people who are meeting patients on the frontline. In A&E departments, in general medical departments, you have to make rapid decisions about where these patients need to go, so that one, that they're cared for appropriately, and two, if they are infectious, other patients are protected from getting infected.
Chris - How does this test work and how have you been able to do in a couple of hours what was previously taking or is still taking laboratories days to do?
Dami - This machine is based on a technique called PCR, or polymerase chain reaction, which can take a copy of genetic information, and copy it many times over so that it can be detected. In clinical practice, we'll take a swab of the throat, or the nose to try and pick up some virus, and then put it in the machine and the machine can then copy this many times over and allowing us to detect it on the test strip. And it can do this in the space of two hours.
Chris - Was it invented for this purpose or is this a case of a re-purposing? You took something that already existed and was being used for something else and realised, Oh, you could do this with it.
Dami - Oh yeah. So it's really the very clever people at Diagnostics for the Real World who then repurposed the machine that was initially developed to test HIV and turned it for use to try and address this problem we're having with the coronavirus pandemic.
Chris - So talk me through then if I came in and sat in the waiting room at a hospital, and one of these machines was running there, what would happen to me in order to give me my diagnosis in two hours? What would you do to me?
Dami - Okay, so we take a swab from the back of your throat with a little cotton ball and we'll take the swab, which hopefully has picked up some virus, if you're carrying some, into a tube of fluid that makes it safe to handle. We then pop this into this machine. It's connected by Bluetooth to a tablet, which tells us when it's ready to read the test, and it reads out the test for us. But also we can have a look at the test strips ourselves and see if are there lines in there to suggest that the test is positive.
Chris - While the machine is testing me though, can you use it to test you, or while it's testing me, is it completely stuck testing me for the two hours it takes to give me my result?
Dami - Yes. So this machine tests only one sample at a time.
Chris - So there is potentially a bottleneck there then isn't there? In the same way that we're currently at a bottleneck with testing people at scale across the UK and other countries, we've still got potentially a bottleneck here. Your results are coming out very quickly, but you're limited by how many machines you've got.
Dami - Yes, exactly that is true. There will be a bottleneck there. However, these machines I think can serve certain populations very well. So if you can imagine in an A&E situation where you have to make a decision, does this patient need to go into a side room for the care they need right now, then it can help to help you facilitate those sorts of questions very quickly.
Chris - And in terms of actually how it works, is it better or at least as good as the tests that we currently have, that are being done in say, Public Health England laboratories across the country?
Dami - The right thing to do with new technology or tests is to evaluate it thoroughly. And this has undergone clinical evaluation at Addenbrooke's Hospital, where we were able to test over a hundred patients, half of whom had confirmed positive COVID-19 and the other proportion who didn't, and it's coming up with a sensitivity of almost 99%, which means that if there were a hundred people in a room who had, COVID-19 it was able to detect 99 of them, which is very good for a diagnostic test. And also it wasn't picking up any tests and calling them positive when in fact they were negative. So in fact it has 100% specificity. So I think there'll be lots of interests from lots of places up and down the country.