Omicron – How reliable are rapid tests for its detection – Nine questions and answers


The advent of the new most contagious Omicron variant of the coronavirus, which is evolving into a new major pandemic wave worldwide, has de facto increased the need for diagnostic tests.

The question for many people is whether rapid tests or Lateral Flow Tests (LFT) “catch” Omicron, especially in view of festive gatherings.

The short answer is that in the case of the new variant quick tests are pretty good, but with the same weaknesses they had shown towards the Delta and the previous variants.

Therefore, as reported by APE-MPE, their false negative results are not uncommon, so it is often necessary to re-test with a new rapid test or, even better, with a molecular test PCR (Polymerase Chain Reaction).

The 9 questions and answers

Here are nine relevant questions and answers, based on the “New Scientist”, so that one has a more comprehensive picture of the issue:

  • I heard that fast tests do not detect the Omicron variant. Is this right;
  • This is not true. Although Omicron has more than 30 mutations, the antibodies used in the rapid tests can continue to bind to proteins and the new variant of the virus. The British health authorities (UK Health Security Agency-Technical Briefing 31) announced a few days ago (on 10/12/21) that, based on the initial laboratory indications, rapid tests have a similar sensitivity to Omicron as it does to Delta.

    However, some people will receive false negative results because, as explained below, the sensitivity of these tests is generally relatively low. It should also be borne in mind that one can be really negative at the time of the rapid test, but a few hours later become infected, especially if in the meantime he has met many people. Therefore, it is better to do the quick test just before someone synchronizes with others, than to rely on a negative quick test that he did a day or two ago, as in the meantime he may have caught the virus, not understood it and so unwittingly to pass it on to others

    2. What is the difference between a fast LFT test and a PCR test?

    Polymerase chain reaction (PCR) tests were the first to be available for coronavirus detection. They work by detecting the genetic material of the virus and are very accurate. Later came the rapid lateral flow tests. Unlike PCR, they detect viral proteins if someone has a coronavirus infection. Most PCR tests need to be sent to a lab, and quick tests can be done at home and give results in minutes.

    3. Are fast tests less good than PCRs?

    Rapid tests are not as good as PCRs at detecting the coronavirus, because PCRs have the ability to multiply the genetic material of the virus many times, so they can detect small amounts of it (viral load in the body). Rapid tests do not have this ability to multiply, resulting in potentially missing infections where coronavirus levels are low.

    4. Can we quantify the difference between them?

    Several studies have evaluated the sensitivity of rapid tests – that is, their ability to detect the virus if present – to be around 40% to 60%, a rate that seems hopelessly low compared to PCR tests, which are very sensitive.

    5. If fast tests are unreliable, what is the point of doing them?

    Scientists point out that people should use a positive quick test result as a “red light” to stop their social activities, but they should not consider a negative result as a “green light” to continue their activities, especially if experience some mild Covid-19 symptoms.

    6. What if the quick test shows just a faint line?

    This indicates that coronavirus protein is present in the body. Positive lateral flow tests may show an overly faint line, something that some people mistakenly perceive as a negative test result.

    7. Why aren’t quick tests recommended if someone has symptoms?

    Authorities, such as the British government, recommend that people take a rapid test only if they have no symptoms, using such rapid tests for daily routine check-ups or for days spent with other people and increasing the risk of infection. If someone has symptoms, they should have the most accurate PCR test. In practice, however, many people resort to the easy solution of quick tests even if they have symptoms, especially when they are mild or not the “official” symptoms of Covid-19. Doctors point out that a person may have coronavirus protein in their body whether they have symptoms or not. Most rapid test studies show that they are somewhat more accurate in detecting cases of people with symptoms than asymptomatic ones.

    8. So is it okay to use a quick test if I have symptoms?

    The crucial thing to remember is that if you have Covid-19 symptoms, a negative quick test result does not give a definite negative answer, so you need to do a PCR test to be more sure that you are not infected. the coronavirus. On the other hand, quick tests on people with symptoms can help them while they wait for the result of a PCR test they did before.

    9. Will there be better fast tests in the future?

    Several other types of rapid tests are in development or already in circulation. Some e.g. they take a sample from the inside of the cheek or saliva and not from the nose or throat, so they are easier to use. But any new fast test, in order to be really useful, must be just as cheap and easy to mass-produce as LFTs.


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