A new mutation of the coronavirus is spreading around the world at a rapid pace, but the symptoms may be milder and, fortunately, a rapid test can detect it, even in the home. Higher rates of illness can lead to higher hospital admissions and even serious cases, so testing is important. According to Miklós Rusvai, PCR and antigen tests are also safe for the detection of omicron.

In early 2022, SARS-CoV-2, a variant of the coronavirus B.1.1.529, which the World Health Organization (WHO) has identified as a variant of SARS-CoV-2, will be spreading faster than any other mutant by 2021. named Omicron on 26 November, after the fifteenth letter of the Greek alphabet. The virus uses the spike protein to bind to the ACE2 receptor, which is how it enters the cell.

Why and how is omicron more contagious?

The spike protein of the omicron contains at least 50 amino acid mutations and about ten non-amino acid mutations, some of which may be in regulatory sequences, compared to the original Vuhan virus. In spike protein alone, the researchers found at least 36 amino acid changes. These changes are responsible for the increased infectivity, as they increase the affinity of the spike protein for the ACE2 receptor and the efficiency of viral entry in the form of membrane fusion. The omicron has dramatically enhanced replication properties compared to earlier variants, probably due to a combination of so-called epistatic mutations. These allow the variant to evade the adaptive immune response, suppress the innate immune response and camouflage itself while replicating in the double membrane scaffold.

Have antigen and PCR tests remained reliable?

Studies are ongoing around the world to see how effective existing tests can be in detecting the new variant.

The PCR tests, as well as the vast majority of quality antigen tests, are completely reliable and can detect omicron mutations, says virologist Miklós Rusvai to B&L Online News and Articles Agency. The US Food and Drug Administration (FDA) is expected to approve the use of the of 28 December according to his entry will monitor and evaluate the potential impact of genetic variants on antigen tests with particular attention. The first results of these studies showed that antigen tests detect the omicron variant, true, the extent to which it may be more sensitive depends on the test. The performance of antigen tests is evaluated using live viral patient samples. The FDA is due in 2021. In early December, it was reported that the US-based Applied DNA Sciences, Meridian Bioscience and Tide Laboratories had signed a molecular (non-antigenic) tests gave false negative results and did not recommend their use by clinical laboratory staff and healthcare providers. In a later, updated statement, it said that Tide’s test had been modified and was now detecting omicron. Major companies that produce rapid antigen tests, including Abbott, BD, Quidel and Siemens Healthineers, have all claimed in their brochures that their diagnostics can detect omicrons. The manufacturers of the e.Diagnosis nasal cavity test and the AmonMed saliva test, both of which are in demand in pharmacies in Hungary, have also today issued an official statement that these tests can safely detect the omicron variant.

Qualitative tests for non-spike proteins are successful

In this context, Miklós Rusvai notes that some antigen tests are inherently more sensitive, some are not, and there may be differences in their mechanism of action. A smaller percentage of antigen tests are directed against parts of the spike protein that are altered in the omicron compared to previous variants. So these diagnostic tools are not working well. However, better quality tests are effective in detecting the omicron variant, including those available in Hungary, as they do not target the spike protein or not exclusively, but also react with other components of the virus.

Since antigen tests mostly detect the so-called N-protein, the nucleocapsid protein, the question may arise whether four mutations in the N-protein might not adversely affect the results of antigen tests. The virologist’s answer is a resounding no: this core protein is the internal protein of the virus, and it is much more conserved, with much less variation. The four mutations are negligible, so such a small change does not affect the sensitivity of the test, and there is no problem for the test system to recognise the antigen. Rapid tests specialised in the detection of N-protein are very reliable,” says the virologist.

Also for these reasons, the FDA continues to support the use of antigen tests, provided that the instructions accompanying the tests are followed. However, it should be noted that these are less likely to detect infections at a very early stage compared to molecular tests. Especially since the incubation period of omicron is only 3 days compared to the 4.3 days of delta, writes drug licensing expert Szabolcs Dobson Dobson in a recent Facebook post.

Repeated testing recommended

This is why Attila Karvalics, CEO of A-Lab Pharma, a leading player in the private retail and institutional testing market (excluding government orders), recommends testing at least weekly, preferably during the fifth wave, probably until mid-February, even without symptoms, and if any mild symptoms have already appeared, repeat antigen testing within a day or two if the first test is not indicated. In fact, you might even want to use two different tests, because there can be differences in quality or even usage problems between test and test. In recent days, the company manager has observed several cases where a high-quality saliva test showed symptoms suggestive of an omicron virus, while a nasal test did not, or conversely, only a top-quality nasal cavity test indicated it. According to the manager, this is due to testing errors but there may also be other physiological reasons, and in his experience tests are often not used according to the specifications.

Important new concepts: mucosal immunity and intermittent, or periodic, virus production

According to Rusvai, a further explanation for the different test results may be that mainly in immunised persons very small amounts of virus are produced, and that the virus production may be “intermittent”, i.e. there is enough virus in the nasal secretions (saliva) today, no virus tomorrow, and enough again the day after to test positive. It also matters when the patient blew their nose (or, in the case of saliva samples, when they consumed food or drink): it is not recommended before testing. In people who have been infected before, mucosal immunity can also be involved: their body secretions (nasal secretions, saliva) contain antibodies that also reduce the chances of detecting the virus. Mucosal immunity does not occur after vaccination, only after infection.

FDA experts stress that if a person has a negative antigen test but is suspected of having a coronavirus infection and is experiencing symptoms, it is important to use PCR, a molecular follow-up test, because it is more sensitive than rapid tests based on antigen detection.

“A reduction in the price of tests would also be desirable, as this could also increase the frequency of testing,” says Karvalic. He said this would be very useful from an epidemiological point of view, as well as to increase the safety and sense of security of the population.

This will also require the cooperation of pharmacies. According to B&L data, most pharmacies currently still sell rapid retail tests at high margins, which somewhat hinders frequent testing. In many cases, even if a distributor has reduced the price, pharmacies do not follow this or only to a lesser extent, so the consumer does not see the positive effects. Domestic pharmacy rapid test margins themselves have typically been at levels that often cost an entire test in the more expensive countries of Europe. It is no coincidence that the GVH has recently launched an investigation into the causes of high domestic prices. The process of price reduction has already started, in a recent promotion of one of the pharmacy chains you can get a high quality antigen test for 2299 HUF, which is already a typical European price.