Reviewers were able to obtain 84 percent of the referenced documents in the ads. However, researchers could only obtain 20 percent of the data-on-file documents, despite repeated requests to the pharmaceutical companies. The companies responded to 37 out of 88 requests for data-on-file, but more than half of the responses indicated that the information would not be provided due to company policy or because it was proprietary.
"We found that almost one-third of the pharmaceutical ads offered no references at all to support medical claims. In addition, most of the data-on-file documents in support of the medical claims were not available from the drug companies," said Dr. David Schriger, study author and professor of Emergency Medicine at UCLA.
In comparison, out of the 400 journal articles, the most commonly cited sources of references included journal articles (88 percent) and books (8 percent). When reviewers tried to obtain the reference documents, 99 percent were available.
UCLA researchers also checked the funding sources of the original research cited in all the ads and of a random sample of 100 journal articles. Out of 294 ad references citing original research, 58 percent had research sponsored by a pharmaceutical company or had affiliated authors, 19 percent were funded by government or charitable sources and 23 percent had no funding statement at all.
In comparison, 8 percent of the original research reported in these journal issues was funded by a pharmaceutical company or had an author affiliated with the company, and 44 percent was funded by a government or charitable organization.
"We found that the majority of the original research cited in the ads to support medical claims was sponsored by pharmaceutical companies," Cooper said.
Schriger noted that improved monitoring and access to references in pharmaceutical ads may be helpful to physicians and policy makers in making more