BMJ readers should know whose words they read

EDITOR—The influence of competing interests arising from funding by the pharmaceutical industry is worrying in the controversy about third generation oral contraceptives.1 At the end of 1998 three major studies without sponsoring from the industry found a higher risk of venous thrombosis for third generation contraceptives, unlike three sponsored studies.2 To date, of nine studies without sponsoring, one study found no difference and the other eight found relative risks from 1.5 to 4.0 (summary relative risk 2.4); four sponsored studies found relative risks between 0.8 and 1.5 (summary relative risk 1.1) (references available on the BMJ's website, www.bmj.com). The sponsored study with a relative risk of 1.5 has been reanalysed several times, yielding lower relative risks; after this failed to convince,3 a new reanalysis was sponsored by another company.4

In 1995 four studies found the same risk. That evidence was sufficient for public health action since equally reliable pills were available. For at least one company the third generation pill secured more than half its revenue. The companies proclaimed that with almost total certainty everything was the result of bias and confounding. Even for a sceptic at the time, that was an unreasonable position: all four studies were reasonably executed and had withstood criticism from the Committee on Safety of Medicines and reviewers of leading journals. Thus, the companies' position ran the …