METM12 plenary talk

The Cochrane Collaboration and current problems in research synthesis

Tom Jefferson, Cochrane Collaboration, Rome

The Cochrane Collaboration is an international not-for-profit network of researchers, consumers and decision makers dedicated to preparing and updating reviews of available research. From humble beginnings the Collaboration has grown to more than 28,000 dedicated people from over 100 countries. Collaborators work together to help health care providers, policy makers, patients, and their advocates and carers make well-informed decisions about health care based on the best available research evidence, by preparing, updating and promoting the accessibility of Cochrane Reviews -“ over 4,600 so far, published online in The Cochrane Library.

Possibly the most difficult problem threatening the reliability of Cochrane Reviews is that of reporting bias.

A recent survey has shown that only 10% of Cochrane Reviews make serious efforts to search for and include unpublished material. The recent series of cases of exposure of sponsor bias overturning our understanding (and in some cases the registration) of important interventions (second-generation antipsychotics, reboxetine, Vioxx, Tamiflu) has shown that reliance on published material can be highly misleading.

Journals (and ultimately research synthesizers) are usually presented with a very short summary of a selected trial which is part of a larger research programme. Given the growing realization that these form a potentially biased evidence base, we may need to develop explicit methods for including regulatory material in systematic reviews or require producers to make all material available to journals (an unrealistic option). First, however, we need to know this is feasible and worthwhile. Tom Jefferson will present and discuss some of these issues on the basis of the oseltamivir (Tamiflu) review, starting with the story of how his team realized their previous Cochrane Review on Tamiflu was biased and how they went about addressing the issue.


Tom Jefferson's professional career has spanned two specialties: general practice and public health. He currently is HTA scientific advisor to the Italian National Agency for Regional Health Services (AGENAS). Tom -œjoined- The Cochrane Collaboration after reading an editorial by Iain Chalmers. He has since co-authored 25 reviews, mainly for the Cochrane Acute Respiratory Infections (ARI) Group. Tom fell into preparing the influenza vaccines and antivirals suite of reviews almost by accident. However, given the international hysteria surrounding influenza this has turned into an almost full-time occupation. Tom and colleagues are at present re-reviewing their previous antivirals Cochrane Reviews using only open access or FOI-requested pharmaceutical and regulatory evidence. The theme of this work is the unreliability of the published record to sustain systematic reviews and the effects of reporting biases.

Read more about Tom Jefferson's work in an article entitled Data diving, published in The Scientist