Antigen rapid tests are an important pillar in the German fight against pandemics. But actually they are far too insecure, says virologist Oliver T. Keppler. He urges that the standard tests be replaced by safer PCR tests – at least in schools and at major events. He explains why he thinks the time has come and which other tests will become more important in the future.
WORLD: In the past few weeks it has happened again and again that people got a false positive test result. In Hamburg, 218 of the 750,000 antigen tests in test centers, daycare centers, schools and nursing homes were positive in the second week of June. The subsequent PCR test then showed that only 44 could actually be confirmed. 174 people had received a false positive result. Can you explain that?
Oliver T. Keppler: This is a problem that virologists have been pointing out since autumn: The test specificity mentioned here is not 100 percent. Many rapid antigen tests say, for example, “98 percent specificity” or even “reliable evidence”: What does that mean in concrete terms? Out of 100 people tested who are not infected, two get a false positive result. The lower the incidence, the greater the bias. But test sensitivity is also problematic. Even with good tests, you can only recognize just under half of the infected. Especially in the highly infectious early phase of the disease, this is a blind eye with a potentially fatal misperception of security.
WORLD: So if I go to the cinema and take the mask off, shouldn’t I feel so safe?