More than a third of the scientific researchers polled in a Canadian study say that they have either experienced or witnessed financial conflicts of interest during clinical trials.
A paper published in the open-access journal Trials says that of the 732 researchers who responded in full, 269 had personally experienced or witnessed financial conflicts of interest over a five-year period.
More than 70 per cent of the cases occurred in industry-funded trials.
Of the 85 respondents who had personally experienced a problem, a third said that it took the form of "recruitment", such as pressure to recruit a specific sample of patients.
A quarter of those polled reported having observed inappropriate "study conduct", such as being asked to put their name to a ghostwritten paper, while the same proportion said they were aware of "personal financial incentives" being offered to colleagues.
An estimated 20,000 clinical trials take place globally each year. The paper notes that Canada, like most other countries, has recommendations in place for trial practices designed to maintain the independence of investigators.
However, it says that adherence to such guidelines is typically low, and that "full adherence to preferred practice was highest when...enforced by an external agent".
Specific concerns are also raised about the prevalence of ghostwriting, which the paper says is used in a "substantial proportion" of trials.
"Less than a third of surveyed individuals indicated that ghost authorship was absent in all of their industry-sponsored trials experience, compared to more than two-thirds for non-industry trials," it says.
It adds that "increased awareness of this issue is important so that investigators understand the potential bias introduced by ghost authors".
The paper, "Investigator experiences with financial conflicts of interest in clinical trials", concludes with a caveat, acknowledging that the sample of Canadian researchers may not reflect the perspectives of investigators globally.
And it notes that "increasingly, clinical research sites are moving to areas such as Eastern Europe and Latin America that may have less experience with clinical trials".