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Coronavirus: why researchers are calling for less reliable and cheaper tests

According to Harvard researchers, too few people get tested in the United States. Cheaper tests would reverse the trend. The adage that the best is the enemy of the good is tragically illustrated in the inadequate screening strategy for Covid-19 in the United States, argue researchers who advocate the adoption of rapid tests at a dollar, imprecise but repeatable several times a week by the entire population.

PCR tests can detect low concentrations of virus. © Photo credit: maxppp

Michael Mina, professor of epidemiology at Harvard, has been campaigning for weeks for what he called shoddy, “bad” or more colloquially “crappy” tests. The idea is to break away from the current model of high-precision molecular tests (PCR tests), which are still too rare in much of the United States, for which people often queue for hours, and wait. days, or even a week, for results.

To test further

He proposed that the US Medicines Agency (FDA) authorize the marketing of rapid tests, done at home from a strip of paper that would change color in a quarter of an hour to give the result, like a pregnancy test.

These tests have low sensitivity, i.e. they miss a lot of positive cases and therefore give a lot of “false negatives”, but for Michael Mina and other experts, this strategy would be more effective in terms of public health since at the population level, the number of identified cases would be greater than at present.

These rapid tests are good on average at detecting people who shed a lot of viruses, that is, when they are very contagious, at the very beginning, while PCR tests are very sensitive and even detect low concentrations of the virus. , which happens at the end of the illness, when people are hardly contagious anymore.

“When you are contagious, the test gets better”

“We are so committed to high-end and expensive testing that we don’t test anyone,” said Michael Mina recently in the This Week in Virology podcast.

Maybe we just need a null test. If it is so cheap that it can be used frequently, then it might detect 85% of people with contagion, instead of less than 5%. “

Harvard Global Health Institute director Ashish Jha returned to the charge on Monday. “These tests are not that bad,” he told reporters. “When you are very contagious, and you have a lot of viruses in your throat and elsewhere, the test improves a lot.” Now, “from an epidemiological point of view, this is exactly the time when we want to detect people.” Even if the rapid test misses half of the cases, it is likely that with two tests per week, it will eventually catch them.

All recall that the current system also misses nine out of ten cases, since relatively few people get tested, according to estimates from the Centers for Disease Control. The FDA has yet to clear any of these strip tests, which are said to cost between $1 and $5. “I fear that our federal government is stuck in an insane thinking pattern for this pandemic,” said Ashish Jha.

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