World Views | New tests could turn tide against coronavirus—if they work

Spain wanted some new rapid coronavirus tests so badly that it bought ones that didn’t work. So did the Czech Republic. The U.K. snapped up millions of them as well, even before scientists have established their accuracy.
Why the frenzy? Countries desperate to curb the pandemic need a clearer picture of the virus and its spread. They’re willing to make a big bet on new testing approaches that look more broadly for signs of infection than existing diagnostics. The stakes are enormous as economies around the globe grind to a halt and the death tally keeps climbing.
“They will be cheaper, easier to use and could be widely deployable,” said Catharina Boehme, chief executive officer of the Foundation for Innovative New Diagnostics in Geneva, a non-profit group that will evaluate the new tests in coming weeks. But “there is a lot of uncertainty still about the performance of these tests.”
Until now, the only way to check whether someone had Covid-19 was to employ a labor- and resource-intensive process that detected the coronavirus’s genetic material in a person’s nose or throat sample. While highly accurate, this so-called molecular testing has drawbacks, including the short supply of key components for them.
The tests also run on complex machinery that require skilled technicians. The resulting bottlenecks have stymied attempts for wide-scale testing, and the tragic consequences are playing out in Milan, New York, Madrid and other hotspots around the world.
By contrast, the rapid diagnostics can be as simple as a home-pregnancy test, delivering results in less than 15 minutes, if they can be shown to work. Their underlying technology is sound, too, used widely for years to test people for influenza, HIV and Zika. The only reason it’s taken this long for them to become available is that developers had to first get their hands on patients’ blood samples to study how they reacted to the coronavirus, and then develop diagnostics that recognize the response.
The new tests come in two varieties. One hunts for so-called antigens – substances that induce an immune response such as the spikes that protrude from the coronavirus’s outer shell – in nose and throat samples. Because they are fast and simple, they are well-suited for drive-through testing centers, doctor’s offices or even homes.
The second type looks for antibodies, which a patient’s body produces in reaction to the viral attack. These tests should tell people if they’ve already beaten Covid-19, even if they never had symptoms or mistook their illness for the flu.
That ability could be a powerful way for policymakers to determine how widely the coronavirus has spread, informing decisions about when to reopen parts of the economy and who is best-suited to get back to work. In hospitals especially, putting doctors and nurses who are not contagious and presumably immune on the front lines could be crucial.
Many governments have decided they can’t wait. The U.K. has stocked up on more than 4 million finger-prick antibody blood tests that could be made available on Amazon.com Inc. and in pharmacies.
Spain bought thousands of antigen tests from a Chinese supplier, only to find out that they’re frequently saying people don’t have the coronavirus when they do. The Czech Republic also found tests it purchased from China to be less reliable than planned.
“Until we have independently validated tests, governments shouldn’t be rushing in to buy millions of them,” said Rosanna Peeling, director of the International Diagnostics Centre at the London School of Hygiene and Tropical Medicine.
For all their potential upside, the new diagnostics may never be as accurate as molecular testing. A patient might test positive for Covid-19 because he developed antibodies against a different coronavirus, such as one that causes the common cold, according to Peeling.
Another risk is simply timing. The body needs about a week to build up enough antibodies to make them detectable – and that process can take even longer in older people or those whose immune system doesn’t work so well. Tim Loh, Bloomberg