No one in all of Europe has carried out a larger serological study than that of Torrejón de Ardoz and now we are beginning to understand why

In the fairground of the Madrid city of Torrejón de Ardoz there are no attractions, nor booths. For days now, on that enormous stretch of asphalt in the south of the city there have only been a dozen white tents, several hundred metal fences and people, many people. More than 100,000 people have passed through the provisional facilities of the City Council and the Ribera Salud company to be part of what some call "the largest seroprevalence study in Europe" and others, as a paradigmatic example of "political marketing" of very dubious utility .

A study that has presented its results this week pointing to an incidence of 20 percent in the city. In practice, almost double what the second wave of the seroprevalence study of the Ministry of Health estimated for the province of Madrid (11.4%). Something that could be explained if we take into account that Torrejón was one of the epicenters of the coronavirus epidemic in Spain, but that could also be explained by the methodological, diagnostic and organizational problems that have come to light in recent days.

And it is that as we approach the great Torrejonean serological experiment everything becomes very confusing and undefined.

Secretism, indefiniteness and suspicious material: this is how the great studio of Torrejón was cooked

The first serious patient in the country lived in Torrejón and, in fact, from almost the beginning it has been suspected that the city of Madrid was the scene of one of the first situations of community contagion. On May 24, Sunday, the plan to launch an initiative to carry out antibody tests on the entire population of the municipality was leaked.

The next day, the Community of Madrid dissociated itself from the initiative and, when in doubt from other municipalities, explained that it was something that was being managed by Torrejón without the participation of the regional government. That same day, Cadena Ser reported that there were already a hundred professionals from Ribera Salud in the Madrid municipality waiting to start the study. Ribera Salud manages the city hospital, but also several health areas in the Valencian community.

This caused that on Tuesday the 26th the Valencia Health Ministry opened a file to Ribera Salud because it had displaced professionals from the health area of ​​Elche-Crevillente and Torrevieja to Madrid without giving details of "the professional categories of those transferred, the travel time, when will they return to their posts "and how they had been replaced. The company's response is that the workers were "volunteers" and were using "their days off, without interfering with daily activities or altering the staff, shifts, schedules or operation of their usual centers at any time."

Meanwhile, the pulse between the Community and the City Council was still running. A pulse that Torrejón would win. On the same day, 27, when according to the leaked posters, the tests were to begin, Isabel Díaz Ayuso, the president of the Community of Madrid, explained that the city council had acquired the tests on their own and that they were studying all the documentation. However, he was in favor and his intention was that this study "be part of a regional serological strategy because there are other municipalities that have also bought them."

"This city and this City Council are very economically modest, but we have decided to prioritize the municipal budget in this action, allocating everything that was going to be used in this year's festivities and in other municipal activities that have been suspended," confirmed the Mayor of Torrejón, Ignacio Vázquez. "It will undoubtedly be the best money invested due to the great concern it has generated in our city, as in all of Spain, and due to the primary need to know our state of health."

Does it make sense to carry out massive tests on an entire population?

From the beginning, doubts between experts and authorities were immediate. There is no clear history of this: no city with more than 100,000 inhabitants had decided to test its entire population. The fundamental reasons are that the efficiency is highly questionable and that they represent a resource expenditure that could be unjustified (given that we have statistical tools that allow us to make effective samples).

"If any community wants to have more detailed data by municipality or other territorial division, it does not seem bad to me that they do so, but it does not make sense that they test the entire population. That they do not waste unnecessary resources if the objective is to know what has happened" , pointed out Fernando Simón, director of the Center for Coordination of Health Alerts and Emergencies. The consensus among public health specialists is that, although this type of campaign can help reassure the population, the truth is that it provides very little information more than a study carried out with representative samples and, on the other hand, costs much more.

Torrejón's last problem: the tests

Finally, the first day of the massive tests was Friday, May 29. That day there were 6,502 residents who underwent tests; Saturday, 21,001; Sunday, 22,644; on Monday, 18,138 and on Tuesday, 18,310 residents. As Antonio Villarreal reported, "more than 100,000 people have passed through the tents at the Torrejón fairgrounds to undergo the test, including a good number of people who do not reside in Torrejón." From teachers and health workers from other areas of the Henares Corridor to military personnel from nearby bases.

Summoned in alphabetical order, during the last days those selected for the study have been able to approach the fairground to take blood samples and do the famous rapid tests. One per person. However, today, Antonio Villarreal and David Brumat published in El Confidencial that the tests that the Torrejón City Council, of the Testsea Labs brand, had bought are "one of the 34 models that the US FDA recommends not be distributed in the territory American or retired. " In contrast, the tests used in the seroprevalence study of the Ministry of Health have the endorsement of several independent reviews.

However, this is only the last "problem" around the Torrejón study that accumulates strong methodological flaws. Things like that are being done not to 'all' citizens, nor to a representative sample; but only those who want to go through the tents (and, therefore, the results do not serve to extrapolate to the rest of the city) or that the lack of clear criteria (or, at least, not published) make them useless to compare them with other studies. If we add to this the false positives and the undetected cases, the great Torrejón study becomes more of a "health action" than a useful job.

But, basically, it could not be anything else because, as the molecular biologist Javier Yanes explained, "even in the case of the most reliable, it is not yet known in detail what immunity to the virus is like. A person who has antibodies against the coronavirus it is not necessarily immune. Even worse, it is quite possible that this person is partially immunized, so that they can contract the virus again without getting sick, but with the ability to infect others. "

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