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A ruling signed by two judges of the Lisbon Court of Appeal questions the reliability of PCR tests, which have been used to identify the presence of the SARS-CoV-2 virus (responsible for the covid-19 disease). The appellants are based on two scientific articles that read “badly” and “irresponsibly”, defend two experts. This is a case that involved four German tourists forced into confinement, during the month of August, in the Azores.
The Relação’s ruling maintains that a PCR test is not enough to have a valid diagnosis of covid-19. Only a doctor can diagnose this or another disease. The judges Margarida Ramos de Almeida and Ana Paramés understand that “given the current scientific evidence, this test is, in itself, unable to determine, beyond all reasonable doubt, that such positivity corresponds, in fact, to the infection of a person ”For the new coronavirus.
“The statement is false,” responds Vasco Barreto, a researcher at the Center for the Study of Chronic Diseases (Cedoc) of the Faculty of Medical Sciences of the Universidade Nova de Lisboa, who considers “irresponsible” the way in which two magistrates of a higher court put into practice causes a scientifically validated diagnostic instrument. “PCR tests have a specificity and sensitivity greater than 95%. That is, in the vast majority of cases they detect the virus that causes covid-19 ”.
This is indicated in a scientific article that is cited in the sentence, but that the magistrates read “totally wrong”, according to Germano de Sousa, former president of the Ordem dos Médicos and owner of a network of laboratories. A study is at stake (“Correlation between 3790 positive qPCR samples and positive cell cultures, including 1941 SARS-CoV-2 isolates”) Whose results were published by Oxford Academic at the end of September.
PCR (“polymerase chain reaction”) tests are the most widely used diagnostic method in most countries to detect the presence of SARS-CoV-2 precisely because they are the most accurate for identifying the virus. This is a technique that amplifies the genetic material of the virus in successive cycles; with each cycle the material doubles. In the cited study, the relationship between the ability of the collected samples to infect cells and the number of cycles required to obtain a “positive” result was evaluated.
“The proportion of samples that were no longer capable of infecting cells kept in culture in the laboratory increased with the increase in the number of cycles required to obtain a positive signal. This is due to the fact that after our body controls the infection, there are fragments of the genetic material of the virus that persist and diminish for days, when the individual no longer represents a danger to others ”, explains Vasco Barreto. Conclusions like these have helped the health authorities of different countries to reduce the mandatory quarantine periods for those infected and to dispense with a negative test to “discharge” a patient.
Now, from reading the article, the judges conclude that “the probability that a person receives a false positive is 97% or more.” According to the research, this only occurs if the cycle threshold is higher than 35 “as is the case in most laboratories in the US and Europe,” the ruling reads. Again, the information is not accurate. For example, in Cedoc, where Vasco Barreto works, for 42% of the positive tests, only 25 or fewer cycles were needed and there is scientific evidence of the high capacity of the virus to spread from “positive” cases to less than 25 cycles.
Another “wrong” evaluation
There is another scientific article cited in the Relação de Lisboa judgment (“False Positive COVID-19 Results: Hidden Problems and Costs”, Published in the scientific journal The lancet) which, for Vasco Barreto, does not point in the direction of the reading made by the judges. “This is a call for more rigorous criteria to define who are the people to whom the tests should be applied,” he says.
Even so, the magistrates rely on this investigation to conclude that “there are so many scientific doubts, expressed by experts in the field, which are the ones that matter here, regarding the reliability of such evidence,” “it would never be possible for this court to determine ”That the German tourist had the SARS-CoV-2 virus.
This assessment is, once again, “wrong” for Germano de Sousa. The German tourist who brought up the case for which the Lisbon Court of Appeal was asked had a positive test after six days in Portugal, after taking a negative test up to 72 hours before entering the country. He was, therefore, “in full swing” when the regional health authority ordered his confinement.
