How are rapid COVID tests holding up as the pandemic enters its fourth year : Shots
Rapid antigen tests are ubiquitous, but some Americans have learned the hard way that a negative test result isn’t necessarily the final word.
Mahmoud Illean/AP
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Rapid antigen tests are ubiquitous, but some Americans have learned the hard way that a negative test result isn’t necessarily the final word.
Mahmoud Illean/AP
As the COVID-19 pandemic enters its fourth year, a negative result on a little plastic at-home test feels a bit less comforting than it once did.
Still, you dutifully swab your nostrils before dinner parties, wait 15 minutes for the all-clear and then text the host «negative!» before leaving your KN95 mask at home.
It feels like the right thing to do, right?
The virus has mutated and then mutated again, with the tests offering at least some sense of control as the Greek letters pile up. But some experts caution against putting too much faith in a negative result.
So it’s only fitting to do a reality check on what those rapid COVID-19 tests, also called antigen tests, can do — and what they can’t.
Is the latest omicron variant tripping up at-home tests?
For the most part, the answer is no.
That’s because as the virus evolves, scientists are mainly seeing changes in its spike protein, which is what the virus uses to attack and enter healthy cells. But the rapid antigen tests aren’t actually looking for that spike protein.
«[The tests] rely on detection of the nucleocapsid protein, which is the protein that is directly encapsulating the viral RNA,» says Dr.
Robin Colgrove, a professor at Harvard Medical School and chair of the Diagnostics Committee of the Infectious Diseases Society of America.
He says this interior protein really hasn’t changed much as the virus has mutated over the years. So, at least for now, the rapid tests can detect it.
Federal health agencies are monitoring the situation in case that changes. The Food and Drug Administration is working with the National Institutes of Health to study just how well the at-home tests work as the virus continues to evolve.
So far, the agencies have identified only one test — the Luminostics Inc. Clip COVID Rapid Antigen Test — that has been rendered less reliable in the face of new variants. And even then, the FDA says «the impact does not appear to be significant.»
Are antigen tests taking longer to show a positive?
Some people report having negative antigen test results for days, despite having a known COVID-19 exposure and the telltale symptoms. Eventually, they test positive, but it can sometimes take as long as a week.
The phenomenon is somewhat mysterious, says Colgrove. He acknowledges that doctors are seeing it, but so far, it’s only anecdotal.
«What kind of an experiment would you have to do to answer that question?» he says, explaining that it would be difficult to study.
Many factors could make it seem as though home tests are taking longer to register a positive result, such as the virus multiplying faster somewhere other than the nostrils in some patients, says Dr. Geoffrey Baird, chair of the Department of Laboratory Medicine and Pathology at the University of Washington School of Medicine.
But Baird says perhaps the biggest factor is human error. After all, people doing these tests at home make mistakes and aren’t trained like those who are doing COVID-19 tests in a lab.
«There’s going to be some people who stick it in their mouth,» he says, explaining that not everyone follows the testing instructions as written. Some people even get mucus on the swab, mistakenly thinking mucus will have plenty of virus in it.
«Actually you don’t want snot on the thing.»
And while, on average, people will get a positive antigen test result around the time they become infectious, Baird says it’s important to remember that there will always be plenty of people on either side of that average: those who test positive much earlier than most and those who test positive much later.
How well do these tests really work?
Antigen tests can be useful in certain situations (more on that in a minute), but Baird stresses that they have their limits. That was true even before the pandemic.
«Similar technology has existed for influenza for years and the recommendation was not to use them,» he says.
Antigen tests look for specific proteins inside the virus. Users typically swab their nostrils, and the tests take about 15 minutes to render a positive or negative result. But these at-home tests need much more virus to generate a positive result than a PCR test, which is done in a lab and involves letting trace amounts of viral genetic material «amplify» over time — usually a day or so.
So even if very little virus is present, there should be enough to trigger a positive result (PCR tests may also keep turning up positive long after someone has cleared the infection).
Both kinds of tests have their advantages and disadvantages. And there are two measures of test performance to know about: specificity and sensitivity.
Specificity is how good the test is at avoiding false positives. And sensitivity is how good the test is at finding the virus.
According to the CDC, antigen and PCR tests are both good at avoiding false positives, but PCR tests are generally more sensitive than home tests. That means antigen tests aren’t all that useful for ruling out COVID-19, but they can be valuable for confirming that cold really is COVID-19.
If you don’t have any symptoms though, don’t count on antigen tests to give you a definitive answer on whether or not you’re in the clear. This is also what researchers found when they took a look at more than 100 studies of antigen tests and published their findings in the Cochrane Database of Systematic Reviews this past July.
«Rapid antigen tests are considerably less accurate when they are used in people with no signs or symptoms of infection, but do perform better in people who have been in contact with someone who has confirmed COVID‐19,» they wrote.
The same researchers also found that not all home tests were equally accurate. Their review included 49 different kinds of tests.
«We saw a lot of variation in the sensitivity of different brands of tests and our overall results combine findings from different studies that evaluated the same tests,» lead author Jacqueline Dinnes from the University of Birmingham said in a podcast about the report.
So what are these tests actually good for?
Even though it seems like a good idea to have everyone take a rapid COVID-19 test the day of a gathering to make sure they’re negative, experts say that’s not how the tests were meant to be used.
«A positive test is almost always true,» Colgrove says. «So in a person with an exposure or a person with suggestive symptoms, if they do a test and it’s positive, you’re done.
You have your diagnosis.»
It’s a slightly different story if you are getting over COVID-19 and are testing to see whether you’re still positive.
But a negative «does not rule out» a COVID-19 infection, according to the Centers for Disease Control and Prevention. If someone tests negative, they’re supposed to take another antigen test 48 hours later to see if it turns positive. And if that person has a known COVID exposure or symptoms, the FDA recommends a third test 48 hours after that.
The best way to use the tests is to know their limits and follow instructions for retesting when you get a negative result.
«In a person who had suggestive symptoms now, in the middle of the epidemic where the prevalence of the infection is high, a single negative test is not enough to rule out infection,» Colgrove says.
If you have COVID-19 symptoms, even if your test is negative, it’s a good idea to be cautious and just stay home.
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Regions are asking for tests — Newspaper Kommersant No. 192 (7154) dated 10/21/2021
State Duma deputies Alexei Kurinny and Sergey Kazankov turned to Deputy Prime Minister Tatyana Golikova with a proposal to expand PCR testing for coronavirus at the expense of the federal budget. In their opinion, it is necessary to give citizens the opportunity to take a test for free at the first sign of SARS. In addition, they are asking for help from employers to establish a testing system at enterprises. Now free testing is the responsibility of the regions and businesses, and they, according to the deputies, can no longer afford such expenses. Note that President Vladimir Putin, at a meeting with the government on Wednesday, instructed to expand testing volumes in order to «timely identify infected people.
» nine0003
Deputies believe that only mass testing at federal expense can stop the virus
Photo: Anatoly Zhdanov, Kommersant
Deputies believe that only mass testing at federal expense can stop the virus
Photo: Anatoly Zhdanov, Kommersant
3 It became known to Kommersant that on Wednesday, Deputy Chairman of the State Duma Committee on Health Protection Alexei Kurinny (KPRF) turned to the Chairman of the Federal Operational Headquarters Tatyana Golikova with proposals for emergency measures against the coronavirus. The letter (Kommersant has it) was also signed by Sergei Kazankov (KPRF), First Deputy Chairman of the State Duma Committee on Small and Medium Enterprises. The deputies note that “one of the reasons for the uncontrolled growth” of the number of infected people is the inability of the healthcare system to effectively interrupt the chains of the spread of the virus. nine0003
In particular, many regions lack the ability to mass-test people with signs of a respiratory infection.
But a significant part of these people (up to 50% according to various sources) are infected with COVID-19,” the appeal says.
As a result, citizens with symptoms of SARS are forced to go to overloaded medical facilities. Many of them freely visit public places and go to work, which «contributes to the rapid spread of coronavirus infection.» nine0003
The deputies point out that the situation could be changed by «regular testing in organized teams that work (study) indoors.» But «only a small number of the most prosperous regions (employers) have such an opportunity.»
Therefore, the authors of the letter suggest Tatyana Golikova «to consider the possibility of significantly expanding the testing of citizens at the expense of the federal budget.»
In their opinion, this «will reduce the cost of the state for the treatment of patients and the cost of the tests themselves with organized centralized procurement.» nine0003
Kommersant was told at the federal operational headquarters that they had not yet received an appeal from the deputies.
Rospotrebnadzor and the Ministry of Health have not yet commented on their initiative. Note that Vladimir Putin, at a meeting with the government on Wednesday, instructed to expand testing volumes in order to «timely identify infected people.»
Recall that now diagnostics in public hospitals are carried out at the expense of regional budgets (including from the funds additionally allocated for the fight against coronavirus to each subject by the government), and at enterprises — at the expense of the employer. nine0003
However, the regions are in no hurry to introduce mass free diagnostics — so far there are only a few examples of such an approach.
So, express testing of everyone with a subsequent PCR test in case of a suspicious result is done in Moscow . Patients with symptoms of SARS are also checked. In addition, the city authorities have begun an experiment on mandatory express testing once every two weeks for students from ten schools.
A week ago Alexei Kurinny proposed to the Ministry of Health Ulyanovsk region to follow the example of the capital.
And about. First Deputy Prime Minister of the regional government Sergei Kuchits replied that it is expensive, and it is better to direct the funds to the priority needs of the healthcare system. Meanwhile, residents of the region complain in the media and social networks that when they contact doctors with signs of SARS and suspicions of COVID-19, they are denied referral for a free PCR test. As a reason, they usually indicate that they are not listed among the “contact persons”.
V Saratov region PCR tests are done only for medical reasons. For the last six months, they have been made to persons with obvious signs of an infectious disease. The government of the Voronezh region said that the issue of rapid testing was raised at the last meeting of the operational headquarters for the non-proliferation of coronavirus infection, but so far it is «under study.» The administration of of the Lipetsk Region said that since the beginning of last week, express testing has been carried out when servicing doctors’ house calls — for patients over 18 years old with typical clinical manifestations of coronavirus.
nine0003
The Crimean authorities , a source in the regional government told Kommersant, are considering the introduction of PCR testing not only in hotels, but also at the airport, as well as on the Crimean bridge. This is primarily due to the hype that has arisen in booking local hotels after reports of the introduction of “covid holidays”. Now tourists who do not have a certificate of vaccination against COVID-19, a certificate of the presence of antibodies or a PCR test, may be completely banned from entering the territory of the peninsula. As an alternative, it is proposed to introduce rapid testing for covid for all visitors. In addition, Crimean officials are discussing the possibility of widespread rapid testing of schoolchildren. Previously, these measures were not resorted to, hoping for voluntary vaccination. Officials promise to find the necessary funds by cutting other budget items, as well as with the help of the federal center and business. nine0003
Associate Professor of the Department of Infectious Diseases of the Peoples’ Friendship University of Russia Sergey Voznesensky supports the idea of expanding the coverage of diagnostics.
According to official statistics, about 7–8% of newly diagnosed patients with coronavirus are asymptomatic carriers, but testing would help to identify them more accurately: “According to some sources, they may account for 50–60% of the number of infected,” Kommersant said. Mr Voznesensky.
Director of the Institute of Health Economics at the Higher School of Economics Larisa Popovich considers PCR testing to be “an expensive and ineffective procedure”: in her opinion, PCR tests can be replaced by cheaper rapid tests or completely removed from the “stereotypical” attitude towards them as a mandatory research method. “It’s better to just react to all cases of fever and respiratory failure as covid and treat them without wasting time on all these studies,” Ms Popovich says. nine0003
Sergey Titov, Ulyanovsk; Natalia Kostarnova; regional corset “Kommersant”
Anti-records and lack of tests: Europe sums up the Christmas holidays
In France, there are already more than 200 thousand infected per day
Coronavirus drug Covid-globulin registered in Russia.
It is produced on the basis of the blood plasma of recovered patients. Clinical studies have shown that the new drug is safe and effective. Meanwhile, abroad the situation with the spread of infection is deteriorating. New anti-records were recorded in Italy, France and the UK.
The disappointing results of the Christmas holidays are summed up in the UK: the number of coronavirus cases has almost doubled, reaching 183 thousand cases per day. The country lacks covid tests. And without them, many who have not yet had time to take root cannot visit cafes, travel or even go to work. nine0003
The Fifth Republic is also breaking records of morbidity — more than 200 thousand infected per day. The introduction of a curfew on New Year’s Eve was abandoned in the country, but the work of cafes and bars will still be limited. So, most likely, the French will have to meet 2022 at home. But if the situation cannot be reversed even then, then the authorities are ready to take even tougher measures — up to the introduction of QR codes in public transport.
«The figures show that the number of cases continues to rise. 208,000 French people have been diagnosed with covid in the last 24 hours. I did the calculations: more than two French people get a positive diagnosis every second in the country. Around the clock, day and night!» — said the head of the French Ministry of Health Olivier Veran. nine0003
Serious restrictions are again introduced in Greece. Residents of the Balkan Peninsula will have time to noisily celebrate the holidays, but from next week catering establishments and nightclubs will only work until midnight. At the same time, personal protective equipment will need to be worn even on the street, and in stores they will be asked to wear not even one — two masks at once. The World Health Organization is confident that the main reason for this spontaneous increase in the incidence was the simultaneous spread of two dangerous strains of the virus at once. nine0003
«We are very concerned that omicron, being more contagious and circulating at the same time as delta, is leading to a tsunami of cases.
