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Experts warn that coronavirus tests have high rate of false-negatives

Several Israeli ministers have promised the shutdown will be gradually lifted, and the economy gradually restarted, after the Passover holiday break, provided that mass testing of the population gives mostly negative results.

However, new research has shown that the tests may not be reliable.

Israel’s 46th “coronavirus fatality,” Rabbi Benzion Kuperstock, a seemingly healthy 63-year-old man, tested negative for coronavirus just four days before he collapsed and died at home. He was re-tested for the virus after his death.

Reports from across the world are emerging that suggest that the tests people are placing so much stock in are not nearly as reliable as we would like to believe.

Defense Minister Naftali Bennett (Yamina) has said several times that mass testing will enable people who have recovered from the virus to get back to work.

In the United Kingdom, the government has placed an order for 17.5 million antibody “home-test” kits, with the Prime Minister saying that they could be a “game changer” that enables the country to get back on its feet.

However, in recent days, Britain’s health secretary admitted in an interview on BBC One that “we still don’t have any [tests] that are good enough.”

According to Dr. David Ho, a leading infectious disease specialist at Columbia University in New York, “The problem is after a couple of weeks, the detection rate remains at about 50%-60%, especially in asymptomatic or mildly symptomatic cases.” In an interview with The Guardian, he explained that “this may not be a fault of the tests, because even using more sensitive methods in the lab we can see the antibody levels are quite low.”

Other experts add that many testing kits have been trialed on patients already hospitalized for the coronavirus, meaning that they are testing people with a very large viral load, around 15% of the total infected population, and perhaps an even smaller proportion. Quest, a company that produces virus tests, told ABC News that its testing kits for coronavirus were fast-tracked by the FDA for approval under what’s called Emergency Use Authorization and therefore “have not been clinically validated. Hence there are no clinical sensitivity and specificity data for any of the FDA EUA assays.”

In an article written for The New York Times last week, Harlan Krumholtz, a professor of medicine at Yale University warned that the problem of insufficiently accurate tests could be greater than many experts realize. “We have very little public data on the false-negative rate for these tests,” he wrote. “Research coming out of China indicates that the false-negative rate may be around 30 percent. Some of my colleagues, experts in laboratory medicine, express concerns the false-negative rate in this country could be even higher.”

ABC News’ medical contributor noted that this might not necessarily be because the tests themselves are not sensitive enough, but could be due to mishandling of the testing process. For instance, if a sample is taken from the throat or nostrils instead of the back of the nose, it might not detect enough viral particles. Alternatively, the test could be administered too early or too late in the progression of the illness, at a time when the virus is either on the rise or the wane. Or the test sample could have been stored incorrectly allowing the viral particles to degrade.

Other doctors note that the differing immune response mounted by people leads to difficulty in producing a mass test that can be used on anyone. Many experts have expressed their concerns that people who have mild cases of coronavirus will not have gained long-term immunity to it, and that they could be susceptible to re-infection if the coronavirus makes a virulent comeback next winter.

Meanwhile, in Norway, mass testing of the population has revealed the bewildering fact that just under five percent of those who suspected they had contracted the coronavirus turned up positive when tested for it.

Header: A laboratory of the University of Pittsburg is working to find a cure for Covid-19, 28 March 2020. UPMC/REUTERS