virus in the throat
Why experts recommend repeated rapid tests because of Omikron
Remain important helpers in the fight against the pandemic: rapid tests
© laborII / Getty Images
Rapid tests also detect an infection with omicron, but probably later than one with other variants. Why this could be and how to achieve the greatest possible security.
The good news is: Corona rapid tests can also detect the omicron variant of the corona virus. This may seem surprising at first glance, but it is ultimately due to the fact that the tests do not target the virus’s spike protein, which is quite clearly altered in Omicron. Instead, the vast majority of commercially available tests look for another corona component that surrounds the virus RNA – the so-called nucleoprotein, N-protein for short.
It is true that omicron also has certain changes in the blueprint for this protein. There are four mutations in total. Nevertheless, early tests, including those conducted by the Frankfurt virologist Sandra Ciesek, showed that the rapid tests basically also work at Omikron. The Paul-Ehrlich-Institut (PEI) now also assumes that “the vast majority” of the rapid tests offered in Germany can detect an omicron infection – provided they meet basic quality criteria (according to the PEI estimate, this applies to 80 percent of the tests ) and the viral load of the person to be tested is sufficiently high. A high viral load is to be expected at the beginning of an infection, whether with or without symptoms, writes the PEI.
Irrespective of this assessment, the PEI researchers want to take a closer look themselves and put the tests to the test with omicron samples. A list of rapid tests that also proven Detect omicron could then be published at the end of February.
Meanwhile, experts are discussing another point – and this concerns the sampling, more precisely: the location of the sampling. The reason: Initial data suggest sothat omicron could be particularly strongly represented in the throat and saliva at the beginning of the infection and only migrate to the nose after some time. Rapid tests, which are taken via a nasal swab, could then “overlook” the first potentially infectious one or two days, so the fear – even though larger amounts of virus are already cavorting in the throat. In the worst case, the affected person, strengthened by the negative test result, would assume that they do not have corona – and spread the virus happily.
Now the fact that a negative rapid test result alone does not offer 100% certainty is not exactly new. Shortly after the first tests went on sale, experts advised not to rely too much on the result, but rather to see the test as an additional protective measure, in addition to other measures such as keeping a distance, ventilation, etc. The gold standard is still the more complex PCR testing.
The US health authority still advises against throat swabs on your own
Nevertheless, health authorities around the world are already considering how self-testing could be made even more reliable given the initial data on Omikron. The Israeli Ministry of Health has already pushed ahead and recommends a double smear test to the population – first throat, then nose. Other authorities are still reluctant to comment. The US Food and Drug Administration (FDA) is currently advising laypersons not to take a throat swab and refers to the lack of data on safety. Wrong results or even injuries could be the consequences.
While the debate on nasal swabs tends to revolve around false-negative results, some experts express concern that throat swabs could give false-positive results. The FDA therefore now wants to investigate whether the layman’s rapid tests are also suitable for throat swabs – i.e. whether they are safe and also deliver reliable results. Approval could soon follow as soon as the data is available.
In Germany, too, the commercially available amateur tests have not yet been approved for a throat swab – they are only intended for use in the front of the nose. They often come with shorter and slightly thicker sticks, which are also difficult to reach with the throat area.
The infectiologist Claudia Denkinger warned in an interview with the “NDR” for another reason against simply using the tests for the nose in the throat: In her opinion, especially when used with saliva, a “completely different composition of the tests is needed, the buffer solution above all”. Possible consequences could therefore be reduced sensitivity of the tests or invalid results.
But how can the best possible security be achieved with the current tests in view of Omikron?
Repetitions bring security
Experts, including the Bremen epidemiologist Hajo Zeeb and the virologist Sandra Ciesek, recommend repeated tests. The approach follows a simple logic: even if the viral load in the nose is not very high at the time of the first test, it is very likely to be on the following day or days.
The virologist wrote that anyone who has symptoms must currently expect an infection a few days ago on Twitter. “Once (negative) is never: people at high risk (symptoms, contact persons) whose antigen test was negative once should be tested again,” says Ciesek.
A second rapid test can be carried out after twelve to 24 hours. Until then, contacts should be reduced. There is also the alternative in the form of a PCR test, according to the expert.