Rapid Tests Can Save Christmas, If You Can Find Them


As terrifying as the rapidly spreading omicron variant is, fewer Americans are expected to have to vacation alone this year for fear of contracting COVID-19. Not only do we have vaccines that save lives. For many people, rapid tests can effectively flag those who are likely to be infectious, allowing others to congregate safely.

Unfortunately, many people won’t be able to take these tests when they would do the most good, right before a vacation visit. We can hope that President Joe Biden’s pledge to send 500 million free tests to any U.S. household that requests them will help address the underuse of an important pandemic control tactic.

The types of COVID-19 home kits the administration has promised to deliver have multiple benefits. They can prevent epidemics and save lives. They can also allow people in fragile health and at high risk of contracting severe COVID-19 to benefit from the necessary human contact. It is tragic that the cost and rarity of these tests prevented such an interaction, given that they have been around for months.

A number of experts say it is misleading to compare the sensitivity of these rapid tests – technically called antigen tests – to PCR tests, for the polymerase chain reaction, which are considered the gold standard. “You can’t really quantify the precision because it depends on the question you’re asking,” said Amesh Adalja, senior researcher at the Johns Hopkins University Center for Health Security.

PCR tests can identify almost anyone who has viral genetic material in their system, even if that person is asymptomatic or no longer infectious. Studies have suggested that rapid tests detect over 90% of cases in people with symptoms; they are not as sensitive to detecting asymptomatic infections – with the most damning studies claiming that they report less than 50% of cases detected by PCR.

But that lacks a crucial point: rapid tests still detect most infections when they are in the contagious stage. Most missed infections, in other words, are too early or too late for the virus to spread to others.

“Home testing has been a holy grail that we have been targeting since the start of the pandemic,” said Nathaniel Hafer, a microbiologist at the University of Massachusetts School of Medicine. He reiterated that it’s hard to quantify their accuracy as it depends on what you’re trying to learn and when you take the test.

Michael Mina, a pathologist who left Harvard School of Public Health in November to join eMed, a testing company, is one of the promoters of rapid tests. While individual PCR tests are considered 98% sensitive – which means less than a 2% false negative rate – as a screening tool to monitor the spread of COVID-19, Mina and two co-authors have argued in an article last year in the New England Journal of Medicine that they fail, catching less than 10% of cases.

Timing is very important because SARS-CoV-2 infections are very dynamic. The virus tends to incubate at levels undetectable by any test for a few days, before growing explosively, often going from undetectable to infectious levels within 12 hours. Omicron can go even faster.

Rapid home antigen testing allows you to get results within minutes of an event or meeting. “Antigen tests are very effective at detecting viruses in the amounts needed to infect someone else,” Adalja said. “You ask, ‘Am I a danger to others? “”

And because timing matters so much in detecting COVID-19, rapid testing may be more accurate than PCR in reducing the risk of super-spread events at private gatherings. They are also suitable for anyone who plans to visit friends or relatives who are undergoing chemotherapy or immunosuppressive drugs after an organ transplant, or who are over 80 years old, or for some reason are not vaccinated. .

On the flip side, if you got infected at a party or restaurant last weekend, had a PCR test on Tuesday, then go to dinner on Christmas Eve with your grandparents. , you put them in danger. A weekend show may not show up that early, and by Christmas you could be very contagious. A quick test just before your visit could detect what that first PCR missed.

The PCR test was designed to amplify viral genetic material – RNA – and therefore can take minute amounts. Rapid tests detect viral proteins, called antigens, and because these aren’t amplified, they won’t detect a new infection that soon, and they won’t stay positive after you stop being infectious.

Rapid tests are a good first course of action if you have cold or flu symptoms. If a test is positive, you can start isolating yourself sooner and alert your contacts, and soon you will be able to benefit from effective antiviral treatments like Pfizer’s Paxlovid. If you have cold or flu symptoms but the test is negative, Adalja from Johns Hopkins recommends going to a drugstore and getting a PCR test before considering yourself licensed.

If you have no symptoms but a quick test before an event is positive, you will need to skip that event no matter what. Experts agree, however, that if you’ve been vaccinated, you can self-isolate for 5-7 days, instead of waiting 10 days and then retesting. This is because people who are vaccinated are contagious for much shorter periods of time.

Most brands of home tests can detect omicron, although Adalja noted that the Food and Drug Administration has reported that three brands – made by Meridian Bioscience, Applied DNA Sciences, and Tide Laboratories – don’t work as well at picking up the new variant. Otherwise, he says, all brands are pretty interchangeable.

One of the problems is that rapid tests are regulated like a medical diagnostic test, and experts say this has led to an onerous regulatory process that has limited supply and passed the cost on to consumers. In much of Europe, rapid tests are regulated as a public health screening tool, which has allowed them to be free and easy to obtain for months.

Part of a political failure is the fact that home tests are hard to come by and that New Yorkers stand in long lines. The Biden administration’s 500 million tests won’t be ready to ship by the New Year, and a website needs to be up and running for people to submit their requests.

How can public health services track test results at home? Tests are often accompanied by a QR code that makes it easier to communicate the results, but even if people don’t follow up, having the information in the hands of those tested is probably more likely to save lives than it would be in the hands of those tested. health status. ministry records. Test takers are in the best position to notify contacts, as most state-run contact tracing efforts have been curtailed or discontinued.

Rapid tests could become a part of the pandemic response that people won’t hesitate to keep even after the disease has become endemic and much of the population stops social distancing and wearing masks. People who are immunocompromised can be at risk for some time, and testing can allow them to enjoy the kind of social life we ​​all need.

Faye Flam is a columnist at Bloomberg Opinion and host of the “Follow the Science” podcast. She has written for The Economist, The New York Times, The Washington Post, Psychology Today, Science, and other publications. This column does not necessarily reflect the opinion of the Editorial Board or of Bloomberg LP and its owners.

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