Paris (AFP)

The horizon is darkening for the authors of the much-criticized study on hydroxychloroquine and Covid-19: the prestigious medical journal The Lancet, which had published it, has distanced itself by acknowledging in a formal warning that " important questions "hovered over it.

The Lancet thus wishes to "alert readers to the fact that serious scientific questions have been brought to (its) attention" regarding this study, the journal says.

The warning was issued Tuesday evening in the form of an "expression of concern", a formal statement used by scientific journals to signify that a study is potentially problematic.

The study in question concludes that hydroxychloroquine is not beneficial to hospitalized Covid-19 patients and may even be harmful.

It had a worldwide impact and spectacular repercussions, in particular pushing the WHO (World Health Organization) to suspend clinical trials on hydroxychloroquine against Covid-19. Similarly, France has decided to ban this treatment.

Published on May 22 in The Lancet, the study is based on data from 96,000 patients hospitalized between December and April in 671 hospitals, and compares the condition of those who received treatment with that of patients who did not. had.

In the wake of its release, many researchers expressed doubts about the study, including skeptical scientists about the benefit of hydroxychloroquine against Covid-19.

- Data -

In an open letter published on May 28, dozens of scientists around the world note that the scrutiny of the Lancet study raises "both methodological and data integrity concerns".

They draw up a long list of problematic points, from inconsistencies in the doses administered in certain countries to ethical questions on the collection of information, including the refusal of the authors to give access to raw data.

These come from Surgisphere, which presents itself as a health data analysis company, based in the United States.

In its press release on Tuesday, The Lancet recalled that an "independent audit on the source and validity of the data has been requested by the authors not affiliated with Surgisphere and is in progress, with results expected very soon".

"It is not enough, we need a real independent evaluation," reacted on Twitter the researcher James Watson, one of the initiators of the open letter.

"There are doubts about the integrity of the Lancet study. In retrospect, it seems that policy makers have relied too much on this paper," commented Professor Stephen Evans, of the London School of Hygiene and Tropical Medicine.

Prior to the controversy over this study, other smaller-scale work had come to the same conclusion without criticizing their methodology.

- "Nickel-plated feet" -

The Lancet study has also been attacked with virulence by the defenders of hydroxychloroquine, often with the keyword #LancetGate on social networks.

Foremost among them is the French researcher Didier Raoult.

"The house of cards is collapsing", he tweeted Wednesday about the Lancet warning, after having already described the study as "messy" and estimated that it had been carried out by "nickel-plated feet" ".

For their part, the authors, Dr. Mandeep Mehra and his colleagues, defend their study.

"We are proud to contribute to the work on the Covid-19" in this period of "uncertainty", one of them, Sapan Desai, owner of Surgisphere, told AFP on May 29.

But this company is at the center of all questions: another leading medical journal, the New England Journal of Medicine (NEJM), also published on Tuesday an "expression of concern" about a study by the same team, carried out with Surgisphere databases.

This study was not about hydroxychloroquine but about a link between mortality from Covid-19 and heart disease.

A French specialist, Professor Gilbert Deray, sees the publication of these warnings by The Lancet and the NEJM as a sign that the two studies are "in the process of shrinking". According to him, such a repudiation would be "a disaster" since these journals are "references".

"These mistakes illustrate that scientific time must be disconnected from that of the media. The urgency of the pandemic does not justify poor studies," he said on Twitter.

© 2020 AFP