RESUMEN
Many studies have shown that there is an association between a positive outcome of clinical trials, economic analyses and systematic reviews, and funding by the manufacturer of the drug of interest. Selective reporting of clinical trial data has been suggested as one of the possible explanations of this so-called funding bias. We conducted a review of the literature to find out if there is any evidence that this selective reporting of clinical trial data occurs. We report the several systematic reviews and cross-sectional surveys, and many case studies of this phenomenon that we found in the medical literature. We searched Medline, Embase and PsycINFO databases for this study besides hand searching BMJ from January 2003 to November 2005. We included systematic reviews, cross-sectional surveys, letters, editorials, comments or news items that referred to actual incidences of withholding, suppression, selective release or selective publication of clinical trial data by pharmaceutical companies