Pharmaceutical companies are more proficient at disseminating the results of clinical research into medical practice than their not-for-profit counterparts, a US study suggests. At the same time, industry-funded trials are considerably less likely to be cited if their outcome is negative.

These were the not entirely surprising conclusions of an analysis by Drs David Cohen and Paul Ridker of the Center of Cardiovascular Disease Prevention at Brigham and Women’s Hospital, Harvard Medical School in Boston, Massachusetts. The researchers used citations rates for cardiovascular trials as a measure of how the medical community responds to study findings from different funding sources.

In the review published in Circulation, Cohen and Ridker assessed 303 consecutive superiority trials of cardiovascular medicine published between 1 January 2000 and 30 July 2005 in the Journal of the American Medical Association, The Lancet and the New England Journal of Medicine. The primary outcome measure was the number of citations per publication per year up to 31 December 2006.

The authors found that the median number of citations per publication per year was 46 for trials funded exclusively by for-profit organisations, 37 for trials jointly funded by for-profit and not-for-profit organisations, and 29 for trials funded by not-for-profit organisations. Industry-funded trials were cited more frequently than federally funded studies even when the studies dealt with similar issues and were published back to back in the same journal.

There were consistently higher citation rates for clinical trials backed by for-profit organisations when these were stratified by journal and trial design features, Cohen and Ridker noted. The distinction was most striking, though, when the new treatment intervention was favoured over the standard of care.

In this subgroup, the median number of citations per publication per year was 52 for trials funded by for-profit organisations and 25 for trials backed by not-for-profit organisations. But where the new intervention was found to be significantly worse than the standard of care, the citation rate reversed to 33 per publication per year for trials funded by for-profit organisations versus 41 for those backed by not-for-profit organisations.

Summing up their findings, Cohen and Ridker suggested that consideration should be given to more extensive promotion of trial results from not-for-profit organisations in an effort to correct the balance of dissemination into medical practice.