A new study published in the preprint open-access journal medRxiv in April 2020 assesses the value of untargeted testing for infection or immunity in COVID-19 vs. high-quality targeted testing in keeping down the number of infections while slowly relaxing lockdown measures.
As leaders over the globe prepare to ease their countries out of prolonged lockdowns, the need for an effective testing strategy has intensified. In the absence of careful execution of relaxation measures, the second wave of infection becomes significantly more likely, and this could exceed the earlier wave due to the presence of the virus in the community.
In the current study, the researchers used a modified SIR model to identify what would happen with imperfect testing on the disease dynamics in a situation when social distancing measures were being relaxed. The model was modified to include quarantined states and its performance was tested using publicly available estimates. The study explored three possible scenarios – immediately ending lockdown measures, continuing the lockdown with immunity passports issued on the basis of antibody testing, and gradual relaxation of lockdown with active viral testing.
The role of testing
The UK, in particular, faced criticism over its low testing capacity early in the pandemic. Even now, many countries seem to be prioritizing quantity over quality when it comes to testing kits. However, when only a small percentage of the overall population is infected, false-positive tests are more likely than positive tests.
This could be a significant barrier to containing the epidemic when the healthcare system is operating under great pressure due to the sheer volume of patients, as is indeed occurring with infected patients being missed.
“The quantity of tests is not a substitute for an effective strategy. Poorly targeted testing has the propensity to exacerbate the peak in infections,” state the authors.
Why different tests need different quality parameters
Testing will be crucial in planning social distancing relaxations. However, all tests are not equal. Antibody tests check whether a person has some immunity against the virus – “have you had it?” while active viral tests test for people who are currently infected – “have you got it?”.
The researchers state that in order to be effective in the current scenario, both tests have to focus on different characteristics. Active viral tests need to maximize their sensitivity – how likely a person who tests positive is to be actually positive, or in other words, how accurate the test is in identifying infection.
If an active viral test is inaccurate and tells people they are not infected when they are, they may behave more recklessly than they would have if they were not sure whether or not they were sick, and in the process infect more people.
Say the researchers, “The capacity for infection screening needs to be significantly increased if it is to be used to relax quarantine measures, but only if it is well-targeted, for example, through effective contact tracing. Untargeted mass screening would be ineffectual and may prolong the necessary implementation of lockdown measures.”
Antibody testing, on the other hand, seeks to identify those who are not likely to get infected because they already have had the disease. The authors say this test should focus on high specificity, or how likely the person is NOT to have had the disease if testing positive. In other words, that means how often the test tells someone they have had the disease when they haven’t.
A false positive here would have serious effects since it tells someone they have immunity to the virus when they don’t.
“Antibody testing, with high specificity may be very useful on an individual basis, it certainly has scientific value, and could reduce the risk for key workers.” the authors say. “But any belief that these tests would be useful to relax lockdown measures for the majority of the population is misguided. At best it is a distraction, at worst it could be dangerous.”
The paper also pointed out that countries which carried out untargeted mass testing early in the pandemic but had much lower case fatality rates might have been reporting a large number of false positives.
In the first scenario – a sudden end to the lockdown – researchers say sensitivity and specificity of testing will have little effect on controlling the virus since the second wave of COVID-19 cases is inevitable if people are allowed to go about with a relaxation of social distancing measures.
In the second – a hypothetical situation with widespread antibody testing and allowing people to move freely on the basis of an “immunity passport” (a positive antibody test certifying that they have some level of immunity to the disease) – researchers say that here too, false negatives would allow re-entry of the virus into the population, and thus send infection rates up.
The third and most likely scenario – the incremental relaxation of social distancing measures – will probably be the most effective in suppressing infection, researchers say. While high infection rates will probably be present for a longer period, it is possible to continuously keep the virus under control.
However, the percentage of the population released in each increment of lockdown relaxation must be carefully determined, because this, in combination with the test capacity and performance parameters, and the prevalence of infection in the target population, are all factors that are crucial in deciding the expected peak of infections following relaxation. This will, therefore, shape the policies regarding the duration of mass-scale social distancing.
In contrast to the WHO’s focus on “Testing, testing, testing,” the researchers conclude, “A bad test is worse than no tests, but a good test is only effective in a carefully designed strategy.”
Covid-19 research scam: Unwanted diversion during pandemic – The East African
The first research scandal of the coronavirus pandemic has created unnecessary distraction around the politically divisive drug hydroxychloroquine, scientists say, as questions swirl around the tiny health care company at the centre of the affair.
On Thursday, most of the authors of major studies that appeared in The Lancet and the New England Journal of Medicine (NEJM) retracted their work and issued apologies, saying they could no longer vouch for their data after the firm that supplied it — Chicago-based Surgisphere — refused to be audited.
At any other time, the matter might have led to hang-wringing within academia, but it has taken on a new dimension as the world grapples with a virus that has claimed some 400,000 lives.
Of particular interest was the paper in The Lancet that claimed to have analysed the records of 96,032 patients admitted to 671 hospitals across six continents, finding that hydroxychloroquine showed no benefit and even increased the risk of death.
Its withdrawal is seen as a boost to backers of the decades-old anti-malarial drug, who include US President Donald Trump and his Brazilian counterpart Jair Bolsonaro.
“It’s very politicised — there is a group, probably not particularly small, who have learned to mistrust science and scientists, and this just feeds into that narrative,” Gabe Kelen, a professor of emergency medicine at Johns Hopkins University, told AFP.
This is despite the fact that even without The Lancet paper, evidence has been building against hydroxychloroquine’s use against Covid-19.
On Friday, results from a fourth randomised controlled trial — carefully designed human experiments considered the most robust form of clinical investigation — showed it had no impact against the virus.
The Lancet, which first published in 1823, is one of the world’s most trusted medical journals.
As a result, the hydroxychloroquine paper had an outsized impact: the World Health Organization, Britain and France all suspended ongoing clinical trials.
But things soon began unravelling after researchers noticed numerous red flags, from the huge number of patients involved to the unusual level of detail about the doses they had received.
Both The Lancet and the equally prestigious NEJM, which had published a paper on whether blood thinners elevated the risk of Covid-19 that relied on the same company, issued expressions of concern — before the authors themselves pulled both papers.
Surgisphere, founded in 2007 by vascular surgeon Sapan Desai, had refused to share data with third-party reviewers, saying it would violate privacy agreements with hospitals.
However, when science news site The Scientist began reaching out to hospitals throughout the US to ask whether they had participated, it found none.
Surgisphere’s internet profile has also raised numerous questions. Only a handful of employees could be found on LinkedIn, and most have now deactivated their accounts.
According to the Guardian newspaper, its employees included an adult model and until last week the contact page on its website redirected to a WordPress template for a cryptocurrency website, leaving it unclear how hospitals could have reached out to them.
Meanwhile Desai, who according to court records has three outstanding medical malpractice suits against him, has written extensively in the past on research misconduct.
“The most serious cause of fraud in medical publishing is manufactured data that authors use to support high impact conclusions,” he said in a 2013 paper.
For Ivan Oransky, who founded Retraction Watch in 2010, the affair is far from surprising, serving instead to highlight systemic issues in science publishing and the way science is reported to the public.
“No one took a hard look at the data,” said Oransky. “But we’ve known about these issues for literally decades.”
Policymakers should get away from the idea of using the results of a single study to inform their decisions, he added, as was the case for the WHO — and the media has a responsibility to place papers in context instead of hyping them up.
The problem also stems from the fact that even leading journals rely too heavily on an honour system, but “you never know when a catastrophe is going to happen, if you’re not willing to put into place some reasonable safeguards,” added Oransky.
As to the future, the current episode is unlikely to serve as a wake-up call, he said. If one journal increases its diligence, more blockbuster papers will start appearing in its competitors.
No new cases of COVID-19 in Manitoba on Saturday – CBC.ca
No new cases of COVID-19 were announced in Manitoba on Saturday.
The total number of cases of the illness caused by the new coronavirus identified in the province is still 300.
The province tweeted the announcement and said Manitoba’s numbers on hospitalizations, recoveries, tests and active cases will be updated again on Monday.
On Friday, there was no one in hospital with COVID-19. Nine cases were still active and 284 had recovered.
Manitoba had done 47,372 tests for the virus as of Friday.
Public health officials advise no new cases of <a href=”https://twitter.com/hashtag/Covid19MB?src=hash&ref_src=twsrc%5Etfw”>#Covid19MB</a> have been identified as of 9:30 a.m. today. The total number of lab-confirmed positive and probable positive cases in MB remains at 300. The online data will be updated on Monday, June 8, 2020. <a href=”https://t.co/QHUWf1HR4d”>https://t.co/QHUWf1HR4d</a> <a href=”https://t.co/Gz8LWOIhD7″>pic.twitter.com/Gz8LWOIhD7</a>
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