"When patients are enrolled, they are randomly assigned to treatment, so that there would not be any bias," Cannon said. "If they are saying it is biased because only one third of patients were women and not half, that seems to not be the right word to describe it.
"Underrepresented would perhaps be better," Cannon continued.
Of the 123 studies, 28 percent did not even have the proportions of men and women reported. Of those that did, almost half didn't report the proportion for all the patients enrolled, "which suggests an important source of missing data," according to Redberg and the other researchers.
"Raw data or statistical analyses rarely were provided, and sex-specific analyses of study primary end points were even less common," they added in the paper.
Resolving this situation may take further action by the FDA, Redberg and colleagues suggested.
The agency has been working on a guidance document for study and analysis of gender differences in cardiovascular device trials; an act pending in Congress could go even further in mandating an end to the disparities, they noted.
"As we move forward, I agree that it is critical to encourage the enrollment of women in clinical trials," O'Donoghue said. "The key is that we don't want women to be deprived of therapies with proven benefit, but rather to find new ways of identifying those women and men who benefit the most."