An India-born cardiologist in the US and his colleagues on Thursday retracted their paper that had claimed hydroxychloroquine treatment increases the risk of death among patients with coronavirus disease, saying they were unable to get independent peer-review of the data used in their study.

The controversial paper by Mandeep Mehra at the Brigham and Women's Hospital, Boston, published on May 22 in The Lancet, a medical journal, had prompted the World Health Organisation to temporarily pause a global clinical trial to test the efficacy of this drug on Covid-19 patients.

The journal had issued “an expression of concern” on Wednesday, saying that although Mehra and his colleagues have commissioned an independent audit of the validity of the data, “serious scientific questions” have been brought to the journal’s attention.

Mehra and his colleagues have now said several concerns had been raised about the veracity of the data and analyses conducted by Surgisphere Corporation, the company through which they had accessed patients’ data from 671 hospitals across the world for their study.

They said the independent peer-review process could not take place because Surgisphere declined to transfer the full dataset required for the process.

“We can no longer vouch for the veracity of the primary data sources,” Mehra and his colleagues wrote seeking retraction of the paper. “We deeply apologize to you, the editors, and the journal readership for any embarrassment or inconvenience that this may have caused,” they wrote.

Their now-discredited study was viewed as a landmark effort as it relied on an exceptionally large dataset of over 90,000 Covid-19 patients worldwide.

Health authorities in many countries have recommended hydroxychloroquine as a “repurposed” drug for treatment of patients with Covid-19. India’s health research agency has also recommended the drug as a preventive medication to high-risk groups such as healthcare workers and household contacts of Covid-19 patients.

The study had claimed Covid-19 patients who receive the drug are more likely to die or develop serious heart rhythm disorders than patients who do not.

The WHO on Wednesday said it would resume its hydroxychloroquine trial, saying an expert panel had reviewed the study and said there are no reasons to modify the trial protocol.