Diagnostics
Covid outbreak and the city subjected to the world’s most severe lockdown, to locate asymptomatic carriers and prevent a resurgence of the virus. Almost 11 million people were tested, with the very few positive cases isolated and their contacts traced. Cases and deaths in the city have remained largely static in the months since.
Despite the costs and complexity of the Wuhan approach, it has proved compelling. In October 2020, Slovakia followed suit, testing 3.6 million people (97% of the eligible population) over the course of a single weekend. Those testing positive (around 38,000 people) were asked to quarantine along with their households, while the rest retained their freedom of movement and were able to go to work. Smaller-scale testing programmes are now being rolled out elsewhere. The UK government is relying on mass testing as a way to keep children in face-to-face education. Since England’s schools opened on 8 March, schoolchildren have been getting tested twice a week. This mirrors similar programmes in Cyprus, which has also rolled out testing in workplaces, and Germany, which now entitles each person to a weekly test. Supposedly, testing everyone at a school or workplace should catch any pockets of infection and stop outbreaks in their tracks, as well as enabling everyone whose results come back negative to go about their lives almost normally, reducing the disastrous social and economic consequences of prolonged lockdowns. Still, mass testing programmes – particularly when they have to screen for asymptomatic Covid – remain an article of some controversy. Questions have been raised about the reliability of the types of tests used across large populations, which come with a significant risk of false positives and false negatives. These errors could either force households to self-isolate, potentially losing income in the absence of any real infection, or embolden people at risk of spreading Covid to act as if they didn’t have it. The UK’s school-testing programme relies on controversial lateral flow tests, designed by Innova, which are cheap and can return results in 30 minutes. These tests have only moderate sensitivity and aren’t very good at picking up asymptomatic infection. When the tests were trialled in a community pilot study in Liverpool, 60% of infected symptomless people went undetected, including a third of those with high viral loads who were at risk of infecting others. Doubts have been raised at how effective they will be at suppressing infection in schools.
Slovakia also used lateral flow tests, which were designed by Roche and SD Biosensor. The initiative is thought to have cut infection rates by around 60% in the absence of a strict lockdown. Unfortunately, this was not enough to prevent a devastating resurgence of the virus, with the country reporting one of the highest per capita death rates in the world by February.
Practical Patient Care /
www.practical-patient-care.com
It is clear that if mass testing programmes are ever going to fulfil their purpose, two conditions need to be satisfied. First, testing cannot be the only thing a country is doing to suppress the virus. Second, the tests need to reach at least some minimum threshold of accuracy while remaining affordable – which may mean thinking beyond lateral flow and polymerase chain reaction (PCR) tests.
“PCR tests cost $100 in the US,” points out Niraj Jha, co-founder of the AI company NeuTigers. “If we go with PCR and there are eight billion of us on this planet and we test every day, that would cost $800bn every day so that the economy can open up. It isn’t feasible.” With their sensitivity and specificity exceeding 95%, PCR tests are regarded as the ‘gold standard’ for detecting Covid-19 infections. But as Jha stresses, while they’re suitable for testing those with symptoms, they require specialist lab equipment, and are therefore too slow and costly to be deployed in a mass-screening approach.
Apps in the deep Jha’s hope is that his company’s new rapid screening app, CovidDeep, could provide an alternative. The app, which uses biometric data, could be used to triage those who need a PCR test. NeuTigers says it is more than 90% accurate in predicting whether a person is virus positive or virus negative – nearly twice as effective as current triage tools like temperature checks and questionnaires.
In conjunction with wearable devices, the app collects data like blood pressure, blood oxygen levels and skin temperature, and checks these against the telltale markers of Covid-19. During the app’s development process, the company collected hundreds of thousands of data points from research participants. It then used neural networks to learn how the virus affected these metrics. The algorithm can spot physiological patterns of Covid even in those who don’t perceive themselves as having symptoms. “To manage the pandemic while going to work and leading a normal life, we need to get tested every day, but with current technologies that isn’t possible,” says Jha. “CovidDeep requires only two minutes of data collection and is accurate. It opens up the possibility we can tackle the pandemic and open up the economy at the same time.”
CovidDeep might be a useful solution for those who want to test themselves regularly in a non-invasive way, but users would need access to an EmpaticaE4 wristband, as well as an off-the-shelf device that can measure blood pressure and blood oxygen readings. It’s unlikely that many individuals would be willing to shoulder this cost, so the app may be better suited to venues that need to test multiple people as a condition of entry. NeuTigers says it is adapting the app to work with connected consumer health products from Fitbit, Apple and others.
23 60%
Asymptomatic Covid infections missed by Innova’s lateral flow tests in a community mass testing pilot in Liverpool last December. The BMJ
3.5m
Number of Covid-19 tests Austria is making available to its citizens every week. Austrian government
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59
