Automated antigen laboratory tests – The little-noticed alternative to PCR tests

No test cassette is required for the antigen laboratory test, the sample is evaluated in the laboratory (picture alliance / dpa-tmn)
Harald Renz heads the Institute for Laboratory Medicine at the Gießen-Marburg University Hospital. For someone like him, tests are nothing more than tools. In the corona pandemic, this means: “In this toolbox we have the PCR and then the antigen tests. And with the antigen tests, we can again differentiate between the so-called rapid tests, which look like pregnancy tests, and so-called automated antigen tests.”

In practice, it always comes down to choosing the right tool. PCR is super accurate, but expensive. The rapid antigen test is inexpensive and works well for people with symptoms who are shedding a lot of viral material. But, according to Renz:

“Patients who are just infected, excrete the virus, small amounts, are not detected with the antigen rapid test and, in principle, fall through the cracks. And this grid is very wide-meshed at Omikron right now, so many of us fail. And now the automated antigen test: It now fills the gap, so it comes very close to the sensitivity of the PCR.”

Swab is taken normally in the nose and throat, but comes to the laboratory

The automated antigen test – the currently little noticed third tool. It also recognizes infected people with a not so large amount of virus because it works differently than the widespread rapid test. Just like this one, the sample is taken from the nose and throat as normal, but then goes to the lab:

“There aren’t 50 people sitting there and they have a lot of cassettes and they drip them in. Rather, this reaction is carried out automatically,” explains Michael Müller, Chairman of the Association of Accredited Medical Laboratories is transmitted – is carried out automatically. And then the reaction takes place, which is something like what happens on the cassette tape.”

More accurate than regular rapid tests

Here, too, the test reacts with certain components of the virus – the “antigen” that gives it its name. This reaction can be measured. This method is actually more sensitive than the rapid test cassettes: at medium viral loads, where the rapid test fails, they still achieve a 90 to 95 percent agreement with the PCR result.

More about the corona test:

Increasing the use of automated antigen testing in the lab would not impact PCR capacity because it requires completely different staff. The question is, are there enough of these machines in the labs for automated antigen testing to make a difference in this pandemic? And are there enough people who could serve them?

Michael Müller answers the question as follows: He says that there has not been a shortage of PCR tests so far. “Therefore, until now, there hasn’t really been a need for antigen lab testing. If these are to be included in the concept, then the laboratories can build up the capacity for laboratory-based antigen tests. It would make a difference when we consider it necessary in a test concept or test strategy that we actually need this amount of testing.”

Can be used in schools or workplaces

In fact, the more precise antigen tests in the laboratory have not yet played a role in the national testing strategy. And Harald Renz thinks it’s time to rethink that, because their use could be helpful in many places: for example in screening in schools or at work. Because here they are trying to filter out the cases that are already infected but – yet – have no symptoms that fall through the rapid test grid.

“Just yesterday I had a very intensive exchange with our city councilor for the daycare and youth area here in Marburg, where we are now considering a small pilot project that we want to do the laboratory antigen test as a pool test in daycare centers instead of the PCR.”

So far no interest from politics

This is one possible application of the automated laboratory antigen test tool. The scientist Harald Renz considers them promising. But translating it into a real strategy is not a scientific question, but a political one.

“We want to record infected people. Let’s just think of the critical infrastructure, hospital, police, fire brigade, schools. And we will continue to get around testing in the future, not around it. That’s why now is the time to set up an infrastructure so that we’ll be ready in summer, autumn and next winter and next year when the topic comes up again. It’s nice when we don’t need it. But it’s better that we’re prepared than sliding back into a situation with a kind of new wave like we’ve experienced a few times now.”

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