Sat. Jan 22nd, 2022


Do we have to blow our noses or throats for tests at home? Can a quick test even detect all of the omicron? Is PCR testing the only result we can trust now?

Guidelines seem to be evolving day by day on how to move towards testing in the Omicron era. Which is a recent real-world study 30 topics followed Possibly after contact with Omicron, PCR saliva tests could quickly detect the Covid-19 case three days before the antigen test, using a nasal swab. The results, which were not peer-reviewed, follow the Food and Drug Administration’s announcement in late December that when they detected Omicron, rapid antigen testing is now underway. “Decreased sensitivity“However, this does not mean that rapid tests do not play a key role in advancing our epidemic response.

It is confusing to the public that the guidelines and tests have been drawn in different directions during the epidemic. Long delay for PCR test results, Lack of quick testing at home, And waiting for more specific science about the Omicron variant has made it all the more difficult to find When and how to check. Nevertheless, public health experts say that as soon as available, rapid tests will be an increasingly important tool for diagnosing and reducing the spread of Covid-19.

So you’re wondering: what’s the point if quick tests aren’t as accurate as PCR tests? Well, quick antigen testing, which makes a look Specific proteins in the Covid-19 virus, Remains highly effective in ensuring positive cases. Simply put, if you test positive in a quick test, you almost certainly have Kovid-19. If you test negative, in some cases, you can still test positive on a PCR test, which is much more sensitive because it tests for genetic evidence of the virus. One expert told Recode that rapid tests may not test positive cases in people who have been vaccinated or who have recently recovered from Covid-19 because they can produce fewer viruses.

Rapid tests PCR tests can reveal a positive case faster than processed labs, as they can take several days to share results with patients, especially during large waves of infection. Perhaps more importantly, quick tests can indicate if someone is contagious enough to spread the virus to others, which is what most people are most concerned about.

“A rapid antigen test is often the most feasible or available option for many, we don’t want the perfect to be the enemy of the good,” says Recode, associate director of global health policy at the Kaiser Family Foundation. He explained that every Covid-19 case that is detected by someone who can test antigens quickly but not a PCR test is a win-win for public health.

Taking quicker tests more frequently makes them more effective. Most at-home rapid test kits are designed to be administered within two days, which is why kits typically include two tests. Since each test is a snapshot of the moment taken, multiple tests help reduce the chances of receiving a false negative.

Of course, all this assumes that you can get your hands on a quick test. In the weeks since Omicron began to spread, it was incredibly difficult to find rapid tests in some parts of the country. These tests are out of stock because neither the test makers nor the Biden administration expected record levels of the Covid-19 case, which quickly increased the demand for testing. The White House to address the deficit Plans to buy and distribute 500 million free quick tests When that happens next week, these tests could help catch more positive cases and reduce the number of people infected with Covid-19.

How accurate is a quick test in the case of Omicron?

The accuracy of a quick test depends on how often you test yourself and whether you want to detect the Covid-19 infection or measure your infection. But if you test positive in a quick test, you should have confidence in your results, assuming you are contagious and isolated for it. At least five days. If you test positive again after five days, the CDC recommends separating for five more.

However, quick tests are not perfect. Studies indicate that the antigen test is less accurate PCR test – This has been the case since the beginning of the epidemic. PCR tests are performed in a lab, where state-of-the-art equipment can detect and amplify the smallest genetic evidence of the cause of the Covid-19 virus. These tests are so specific that patients can test positive for weeks after recovery. It is no longer contagious. Quick test results may vary depending on how much virus was in the patient’s nose at the time of sampling and how far away they are from their infection.

Scientists explain the difference between a rapid test and a PCR test in two ways: Specification, Which reflects the false-positive rate and sensitivity of a test, which reflects the false-negative rate of a test. Both PCR and rapid testing have high specificity, which means their positive results are extremely reliable. But while PCR tests have almost perfect sensitivity, rapid antigen tests have about 80 to 90 percent sensitivity. This means that faster tests produce more false negatives than PCR tests.

Omicron makes the test more complicated. According to preliminary research by the FDA and other scientists, the sensitivity to rapid testing in the case of Omicron may be even lower. Another problem is that omicron can propagate More in the throat than in the lungs, And may take longer to show up in nasal samples for Covid-19, even if one has symptoms. It is possible that vaccinated individuals and those who have recently recovered from Covid-19 are more likely to find false positives in rapid testing because they produce fewer viruses overall.

Pablo Penaloza-McMaster, a viral immunologist at Northwestern Medical School, told the record that “tests at home are most effective when the person has a high viral load, at a time when the person is more likely to be infected.” Home tests are still able to detect infections by Omicron because they detect a part of the virus that does not change much. “

Study separately from the two Health Safety Agency of the United Kingdom And Researchers in Australia Antigen tests have been shown to be as sensitive to the Omicron variant as the previous strain of Covid-19. Again, the FDA still recommends rapid testing to diagnose positive cases, and test makers say they are confident in their product’s ability to detect omicon. When early Research Saliva tests indicate that Covid-19 can be detected more quickly, with most PCR tests at the moment and all FDA-approved emergency use sitting at home using nasal samples.

How to use quick tests in low-ideal situations

Which brings us back to the question of whether nasal swabs should be stuck in your throat. There is evidence that saliva samples may be a quick indicator of a Covid-19 case, but this does not mean that you should stop following the instructions that came with your test kit. The FDA says people should not use rapid antigen tests to clean their own face. Some experts say you might consider doing this anyway, noting that other countries, including the United Kingdom, have quickly approved antigen testing that uses throat swabs and Has issued very careful instructions on how to do this.

Michael Mina, an epidemiologist at Harvard, told a news conference on Thursday, “I personally get the best sensitivity when I use over-the-counter tests at home to blow my throat and nose.” “There are risks involved, but biology tells us they can get better sensitivity earlier.”

But now the concern with the quick test kit is that people are blowing their noses, but how often they are blowing their noses. A single test can miss a Covid-19 case and produce a false negative, but two tests performed within 24 to 36 hours reduce this risk. The faster you take the test, the less likely you are to have a false negative, and the more times you test negative in multiple days, the more confident you will be that you are not spreading Covid-19.

Still, the biggest problem right now is the quick test Expensive and hard to find. Pharmacies have limited the number of test kits that people can buy, and many have sold out completely. A single test can cost upwards of $ 10, which means that regular self-testing can be expensive. The opportunists have even stockpiled tests and Involved in price increase, Which has exacerbated the deficit.

If you do not have enough tests to test yourself regularly, it is better to test yourself before seeing weak people, he said Dead Espinal, A professor who heads the Arizona State Testing Diagnostic Commons and a board member from Orasur, the test maker, told Rekod. “I am moving towards a weak person [or] I’m going to a healthcare setting, and I need to get tested in advance. ”

For now, the best test kit is the test you can get (wired) A simple list Of currently available brands). If you plan to go somewhere and do not want to spread the virus, you should have a quick test the day before the trip and then a second test immediately before you go. If you only have one quick test, take it before you see people.

It should be easier to test yourself as more tests become available. The White House will distribute 500 million free quick tests Starting later this month, People with personal insurance will also be able to get their fast test purchase rewards Starting next week. You should also check with the local health department, as they are distributing free tests.

Although rapid testing conditions are still less than ideal, there are other techniques we can use to protect ourselves and others from Covid-19, such as getting vaccinated, boosted, and wearing a mask. And if you find some quick tests, go ahead and grab them. These can only come in handy, especially if you use them properly.

Updated, January 7, 10:30 am: An earlier version of this story misrepresented in an example that rapid Covid-19 testing between vaccinated individuals and those with immunity from a recent infection may appear frequently. False results are false negative, false positive.



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