The new antibody tests COVID-19 which provide a result on the spot is not reliable enough for that they should cease to be used immediately, according to new research conducted by Canadians. The research, which was published Wednesday in The BMJ, involved a review of all known studies on the effectiveness of the antibody tests.
Find reliable information has not been easy. The researchers found 40 studies for review, of which 70% came from China. Most of the studies were shown to have been designed to create a bias in the results, and about half had not been the subject of a peer review.
However, the researchers say that the studies were sufficient to come to a clear conclusion: there are “major weaknesses” in the existing evidence supporting the use of blood tests that do not treat their samples in the laboratory.
“The evidence does not support the continued use of serological tests at the point of service existing for the COVID-19 “, they wrote.
Serological tests are used to determine if a person has developed antibodies against COVID-19, which suggests that she has already fought the disease once, and that it is theoretically immune against a second infection.
They can also be used to diagnose active cases of COVID-19, although the medical standard for this is to use molecular tests, which require laboratory processing, which makes them more expensive and with longer delays before providing the results.
The increasing deployment of serological tests has led to the idea of ” passports of immunity “, where the results of tests of antibodies that could be used by governments to track what citizens have and have not developed the antibodies.
Although this idea may seem promising – to enable those who have already had COVID-19 live their lives with limited restrictions, while those that have not may remain isolated – the health authorities, including the world health Organization and the chief administrator of the public health agency of Canada, have been more negative. arguing that the passports of immunity should not be taken into consideration as there is no additional evidence of the duration of life of the antibody.
There are also other objections, from privacy concerns to potential discrimination, passing by the possibility that some people become infected intentionally, in order to develop immunity.
The new research pours yet more cold water on the idea, noting that the serological tests have error rates relatively high. These errors can take the form of false positives, where the disease would be found in someone who does not, or false negatives, when the antibodies of an infected person does not appear in the results.
The researchers found that the serological tests studied had a relatively successful when it was to avoid false positives, which occurred between 0.3% and 3.4% of the time.
False negatives are a much bigger problem, certain tests will only detect, not the antibodies COVID-19 in up to 34% of all those who had been infected.
The tests which had the most false negatives were those of the variety of immunoassay lateral flow (LFIA) – the type contemplated for use in the passports of immunity because of his lack of need for laboratory processing makes it faster and less expensive than the alternatives.
In the United States, the Centers for Disease Control and Prevention have warned that the antibody tests may give false results up to 50% of the time.
According to the researchers, their results suggest that if the tests of LFIA are administered to 100 people who have had COVID-19, and 900 who did not, 34 of those who have the antibodies will say, wrongly, that they have not, and 31 of those without will be falsely told that they are doing it.
“Overall, the poor performance of serological tests exist for COVID-19 raises questions about the usefulness of the use of these methods for medical decision-making “, they wrote.
“While the scientific community should be praised for the pace at which new serological tests have been developed, this review underlines the necessity of clinical studies of high quality to assess these tools. ”
The research team was headed by McGill University in Montreal and also included contributions from the University of Sherbrooke, University of British Columbia, the State University of Rio de Janeiro, and the Harvard Medical School.