PCR, the most common test to detect coronavirus, has a high sensitivity. So much, that sometimes I could be throwing positive in people who are no longer infected.
According to a study by the University of Oxford collected by the BBC, the tests could be detecting fragments of the virus that are already dead.
Most people remain infected for about a week, but the diagnosis can still be positive. weeks later.
Carl Heneghan, one of the study’s authors, says that instead of being positive or negative, the tests should be capped, so small amounts of virus do not give positive.
This detection of dead viruses could explain, according to Heneghan, why hospitalizations remain stable in countries with a second wave of very high infections.
The Oxford scientists analyzed 25 studies, in which they took the positive samples and observed if the virus grew, which is called a ‘viral culture’.
According to the researchers, PCR throw a ‘yes’ or a ‘no’, but it does not say how much virus was detected or whether the infection is active or not. Thus, a person with a high viral load and a person with dead virus fragments give the same result.
If there was a test that said if the virus is active or not it would avoid unnecessary quarantines and it would provide more reliable data on the pandemic.