How much can you trust express tests?

A negative coronavirus test result is reassuring. But how justified is it, after all, 20% of such tests, that is, every fifth, have not been tested for effectiveness?

State publication Deutsche Welle figured out what was wrong with express tests designed to carry out quick control. In Germany, since the beginning of this year, they can be purchased not only in pharmacies, but even in supermarkets. It is convenient to do them before work or visiting relatives to make sure that a sore throat, for example, is not the initial symptom of coronavirus. A negative test also serves as a pass to some institutions or catering establishments, even for vaccinated citizens. And in general, having received a negative result, many feel more confident and calm.

However, a group of scientists from the Robert Koch Institute, the Paul Ehrlich Institute and the Charite clinic in Berlin argue that you should not particularly trust a negative test result. They checked many of the rapid tests offered to buyers in Germany and found that 20% of the results were wrong. The results of the study are published, and it follows that 26 out of 122 rapid tests did not meet the requirement, which suggests a minimum of 75% sensitivity.

The Ct value is a measure of the number of replication cycles performed in the laboratory before the detection of SARS-CoV-2 genetic material. The lower the Ct value, the higher the viral load. If it is 25 or less, then it indicates a very high viral load, that is, the person is extremely infectious. With a Ct value of 25 to 30, we are talking about a high viral load, and a value from 30 to 36 indicates a moderate one. In cases where the viral load was very high, every fifth test did not detect an infection.

Usually, when testing for coronavirus, a swab is taken from the patient’s nose or throat. If a small amount of viruses is found in the sample (usually in cases of the onset of the disease or, conversely, at the stage of recovery, or if a person drank a lot of liquid before the study), then express tests, to put it mildly and figuratively, can be “cunning”.

If the rapid test shows a positive result, a more reliable PCR should be used immediately. With this type of examination of the sample, the genetic material of the SARS-CoV-2 virus is detected using a polymerase chain reaction – a small amount of the virus is quite enough for it.

Why does the effectiveness of express texts fail, are they not checked? If you are standing, then sit down so you don’t fall: Rapid test makers have every right to sell them without independent external quality testing. Moreover: they have the right to personally issue a certificate that their product meets all the requirements of EU standards! This is stated on the website of the Paul Ehrlich Institute, which should be responsible for the registration of vaccines and monitoring in Germany in this area:

“According to the current EU directive for drugs for medical laboratory research (in vitro diagnostics, IVD), which currently regulates the admission of IVDs to the European market, manufacturers can independently certify COVID-19 tests as low-risk IVDs and refuse independent verification. before launching them on the market. “

And what quality can we talk about in this case? At the same time, the existing regulations (independent confirmation of efficiency), according to the Paul Ehrlich Institute, will be in effect until May 2022 (at least). Only from next summer, IVDs, apparently, will become drugs with a high level of risk, and in this case, before registration, they will have to undergo quality control, moreover, in independent laboratories.

Are the tests we trust useless in this case, you ask? Of course not. Indeed, in addition to the unreliable 20%, there are another 80% that help to quickly identify the infected and prevent the rapid spread of coronavirus.At the same time, in cases of high viral load, when the carrier of the virus poses an increased danger to society, express tests are practically not mistaken.

In any case, you should not rely on the results of express tests, since with an asymptomatic course of the disease, they can not see the infection. If the result is positive, the PCR test will help establish the truth.

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