Can omicron perform a quick test? Should I wipe my throat? Covid test questions, answered.

Should we wipe our nose or throat when testing at home? Can the quick test even detect omicron? Is the PCR test the only result we can trust now?

Guidelines on how to test in the omicron era seem to be increasing day by day.A recent real-world study showed 30 subjects tracked Researchers who may be exposed to omicron have discovered that PCR saliva testing can detect Covid-19 cases three days before rapid antigen testing using nasal swabs. These findings, which have not been peer-reviewed, were announced at the end of December by the U.S. Food and Drug Administration. Although they did detect omicrons, the rapid antigen test may now have “Reduced sensitivity. “But this does not mean that rapid detection will not play a key role in our future pandemic response.

For the public who was drawn to several directions in terms of guidance and testing during the pandemic, all this is confusing. Long delays in PCR test results, Lack of quick tests at home, And waiting for clearer science on omicron variants make it harder to figure out When and how to testNonetheless, public health experts say that as more tests become available, rapid testing will become an increasingly important tool for diagnosing Covid-19 and reducing its spread.

So you might be wondering: What is the point if rapid detection is not as accurate as PCR detection?Okay, quick antigen test, it looks for a Specific proteins on the Covid-19 virus, Is still very effective in confirming positive cases. In short, if you test positive in a rapid test, you are almost certain that you have Covid-19. If your test result is negative, in some cases, you may still test positive in the PCR test because the PCR test detects genetic evidence of the virus and is therefore more sensitive. An expert told Recode that rapid testing may not find positive cases in people who have been vaccinated or recently recovered from Covid-19 because they may produce fewer viruses.

Rapid tests can also find positive cases faster than laboratories handling PCR tests, because it may take several days for them to share results with patients, especially during large waves of infection. Perhaps more importantly, rapid testing can show whether a person is contagious enough to spread the virus to others, which is what many people worry about the most.

“Given that rapid antigen testing is usually the most viable or available option for many people, we don’t want perfection to be the enemy of good things,” said Joshua Mishaw, deputy director of global health policy at the Kaiser Family Foundation, telling Recode. He explained that every Covid-19 case detected by a person who can undergo rapid antigen testing but not PCR testing is a victory for public health.

Performing quick tests more frequently also makes them more effective. Most home rapid test kits are designed to be performed within two days, which is why the kit usually contains two tests. Since each test is a snapshot of the time it is in progress, multiple tests help reduce the chance of receiving false negatives.

Of course, all of this assumes that you can perform a quick test. Within a few weeks after omicron began to spread, it was difficult to find quick tests in certain areas of the country. These tests are out of stock because neither the test manufacturer nor the Biden government anticipated the record level of Covid-19 cases, which has increased the demand for rapid tests.In response to the shortage, the White House Plan to purchase and distribute 500 million free quick tests In the next few weeks. When this happens, these tests can help find more positive cases and reduce the number of people infected with Covid-19.

When it comes to omicron, how accurate is the quick test?

The accuracy of the quick test depends on how often you test yourself and whether you want to identify Covid-19 infection or measure your infectivity.However, if you test positive in the rapid test, you should trust the result, assuming you are contagious, and quarantine At least five daysIf you test positive again after five days, the CDC recommends isolation for another five days.

However, the quick test is not perfect.Research shows that antigen testing is not as good as PCR test -This has been the case since the beginning of the pandemic. PCR testing is carried out in a laboratory where advanced equipment can identify and amplify even the smallest genetic evidence of the virus that causes Covid-19.These tests are so precise that the patient can actually test positive within a few weeks of recovery, and No longer contagiousAt the same time, the results of rapid tests may vary depending on the amount of virus in the patient’s nose at the time the sample was taken and the degree of infection.

Scientists explained the difference between rapid detection and PCR detection from two aspects: Specificity, It reflects the false positive rate and sensitivity of the test, and it reflects the false negative rate of the test. Both PCR and rapid testing have high specificity, which means that their positive results are very trustworthy. However, although PCR tests tend to have nearly perfect sensitivity, the sensitivity of rapid antigen tests is often around 80% to 90%. This means that rapid tests tend to produce more false negatives than PCR tests.

Omicron makes testing more difficult. According to early studies by the FDA and other scientists, the sensitivity of rapid detection may be lower for omicron cases.Another problem is that omicron may spread More throat than lungs, Even if someone has symptoms, it may take longer for Covid-19 to appear in a nasal sample. People who have been vaccinated and those who have recently recovered from Covid-19 are likely to find more false negatives in rapid tests because they generally produce less virus.

Pablo Penaloza-MacMaster, a viral immunologist at Northwestern University School of Medicine, told Recode, “When a person’s viral load is high, testing at home is most effective, and at this time the person is more likely to spread the virus.” Home testing is still Omicron infections can be detected because they target a part of the virus and will not mutate so much. “

Separate research British Health and Safety Agency and Australian researchers It was found that the antigen test is as sensitive to the omicron variant as it is to the early Covid-19 strain. Similarly, the FDA still recommends rapid tests to diagnose positive cases, and test manufacturers express their confidence in the ability of their products to detect omicron.Although early Research Indicating that the saliva test may detect Covid-19 more quickly, most of the current PCR tests and all available rapid home tests that are authorized by the FDA for emergency use use nasal samples.

How to use quick tests in less than ideal situations

This brings us back to the question of whether a nasal swab should be inserted into the throat. There is evidence that saliva samples may be a faster indicator of Covid-19 cases, but this does not mean that you should stop following the instructions that come with the test kit. The FDA stated that people should not use rapid antigen tests to wipe their mouths.Some experts say you can consider doing this anyway, and point out that other countries including the United Kingdom have approved the use of throat swabs and Very careful instructions on how to do this are posted.

Harvard University epidemiologist Michael Mina said at a press conference on Thursday: “When I take an over-the-counter test at home, I personally wipe my throat and nose to get the best sensitivity. “There are risks associated with this, but biology does tell us that they may get better sensitivity earlier.”

But the problem with rapid test kits is not how often people wipe their noses, but how often they wipe their noses. One test may miss Covid-19 cases and produce false negatives, but two tests within 24 to 36 hours can reduce this risk. The faster you test, the lower the chance of false negatives, and the more negatives you test in multiple days, the more confident you are that you are not spreading Covid-19.

Nevertheless, the biggest problem at the moment is rapid testing Expensive and hard to findPharmacies limit the number of test kits that people can buy, and many kits are sold out. The cost of a single test can also exceed $10, which means that testing yourself on a regular basis can quickly become expensive.Opportunists even hoarded tests and Participate in price bidding, Which exacerbated the shortage.

If you don’t have enough tests to test yourself on a regular basis, it’s best to test yourself before seeing the vulnerable, say Mara Aspinal, The professor who leads Arizona’s test diagnostic commons and a board member of test manufacturer Orasure, told Recode. “I’m walking towards a vulnerable person [or] I want to enter a medical institution, so I need to be tested in advance. ”

Currently, the best test suite is the one you can get (wired Handy list Currently available brands). If you plan to go somewhere and don’t want to spread the virus, you should have a quick test one day before the trip, and then a second test immediately before departure. If you only have one quick test, take it immediately before you see someone.

As faster tests become available, testing yourself should become easier.In addition to the 500 million free rapid tests that the White House will distribute Start later this month, People with private insurance can also be reimbursed for their quick test purchases Start next weekYou should also consult with your local health department as they may distribute free tests.

Although the rapid test situation is still not ideal, we can use other strategies to protect ourselves and others from Covid-19, such as vaccinations, boosters and wearing masks. If you happen to find some quick tests, go ahead and grab them. They may come in handy, especially if you use them correctly.

Correction, 10:30 AM, January 7: An earlier version of this story misrepresented a false result in an example that may be more common in rapid Covid-19 testing in people who are vaccinated and those who are immune to recent infections. A false result is a false negative, not a false positive.