Nose or throat swab? The following errors lead to incorrect corona test results

Rapid antigen tests are routine for many people. Do the corona tests reliably detect omicrons? Does a swab from the throat or nose falsify the result?

Munich – With the corona self-tests, a large number of infections are also detected at Omikron. Some rapid test kits require a nasal swab, others a throat swab. The assumption that swabs from the throat are more accurate than those from the nose is currently spreading. Are throat swabs really more reliable in detecting omicron infection?

False test results can occur with the rapid antigen tests for use at home. The British doctor Dr. Nathan Hudson-Peacock from London has uncovered the three most common mistakes that lead to an incorrect test result. The most important things about the self-tests at a glance:

Can rapid antigen tests detect Omicron?

Rapid antigen tests also work at Omikron. The tests suggest the so-called nucleocapsid protein of the Sars-CoV-2 coronavirus. The Paul Ehrlich Institute (PEI) reports that the quick tests are also suitable for Omikron. Even if the N protein has changed somewhat. However, there are differences in the rapid corona tests. The PEI has published a list of the most reliable antigen tests. In addition, the PEI authority is planning to publish a list of the corona tests that identify Omikron particularly well. The Frankfurt virologist Sandra Ciesek tweeted that Omikron had hardly appeared that rapid antigen tests reacted reliably.

Corona quick test: nose swab or throat swab at Omikron?

As already mentioned, there are quick tests that require a nasal swab. Reports are also piling up on social media that people with cold symptoms have tested negative after a nasal swab and then tested positive after a throat swab. They fueled a smear debate. There are recommendations for a quick nasal swab test to also insert the swab into the throat. So to do a combined swab in the nose and throat.

So far there is a preliminary Study (Preprint December 24) from South Africa, according to which it makes a difference whether the swab was taken from the nose or throat. An omicron infection was more likely to be missed in a nasal swab. Saliva swabs are to be preferred for omicron detection. Omicron appears to be detected earlier in the throat than in the nose. While the coronavirus wild type and the variants alpha and delta are increasingly found in the nose at the beginning of an infection.

Experts advise against simply taking swabs in the throat during self-tests. The results could be falsified by the application. The US drug authority FDA and the PEI emphasize that they do not deviate from the instructions for use for the respective tests. The industry service warns that adding too much saliva could falsify the result pharmacy-adhoc. The rapid tests in the front of the nose are still very accurate in asymptomatic people. According to the specialist magazine, many professional tests can be used for the nose and throat.

Corona rapid tests: Errors that can lead to incorrect test results

Most are already professionals at Schnelltest. But there are mistakes that lead to false test results. The British doctor Dr. Hudson-Peacock warns of the three most common mistakes – some people take it easy with the tests, especially in their own four walls. Some substances, such as fizzy drinks, can cause false positives, Hudson-Peacock explains in the British magazine Metro.

• Read the instructions correctly: Many people do not read the instructions for use for the rapid test properly. According to Hudson-Peacock, this can lead to incorrect results.
• Home preparation is also required for most rapid test kits: do not eat or drink for 30 minutes before the test, blow your nose, and wash your hands before taking the swab sample.
• A common user error in most tests: swab samples are always taken from the wrong place. Most test kits only require a nasal swab. In his opinion, a throat test could then lead to false positive test results. But the one from the nose would be negative.

With a rapid corona test: Pay attention to the line – interpret the result correctly

dr Nathan Hudson-Peacock, who works as an emergency medicine doctor at a London hospital, also shares the pitfalls of testing from home on his Instagram account with the name expedition_doctor. The doctor also wants to make his followers aware of the importance of a test result. It is also important to read the result correctly. A line, however faint, that appears parallel to the letter “T” within 30 minutes of taking the test indicates a positive result. The test subject should then self-isolate. To be sure, he thinks a second test makes sense.

But if this line appears after 30 minutes, it does not indicate a positive test result. However, Hudson-Peacock urges caution. Everyone should follow the precautionary measures, especially indoors. Wear a mask, keep your distance and wash your hands regularly. And of course getting vaccinated against Corona.

Omicron: These are the most common symptoms of an infection

Omicron cases are spreading rapidly in Germany. The Robert Koch Institute (RKI) has published data on the most common omicron symptoms.(ml)