MedicalResearch.com Interview with: Dr Su Golder PhD Research Fellow Department of Health Sciences University of York MedicalResearch.com: What is the background for this study? What are the main findings? Response: Serious concerns have emerged regarding publication bias or selective omission of outcomes data, whereby negative results are less likely to be published than positive results. There remains considerable uncertainty about the extent of unpublished data on adverse events beyond that reported in the published literature. We aimed to estimate the potential impact of additional data sources and the extent of unpublished information when conducting syntheses of adverse events. We found that less published papers contain adverse events information. The median percentage of published documents with adverse events information was 46% compared to 95% in the corresponding unpublished documents. There was a similar pattern with unmatched studies, for which 43% of published studies contained adverse events information compared to 83% of unpublished studies. We also found even when adverse events are reported in the published and unpublished versions of the same study that the numbers of adverse events do not always match The percentage of adverse events that would have been missed had each analysis relied only on the published versions varied between 43% and 100%, with a median of 64%. Lastly we found that inclusion of unpublished data increased the precision of the pooled estimates (narrower 95% confidence intervals) in three-quarters of pooled analyses, but did not markedly change the direction or statistical significance of the risk in most cases. (more…)