MedicalResearch.com Interview with:
Dr Su Golder PhD
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 There remains considerable uncertainty about the extent of unpublished data on adverse events beyond that reported in the published literature. We aimed to estimate the potential impact of additional data sources and the extent of unpublished information when conducting syntheses of adverse events.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median percentage of published documents with adverse events information was 46% compared to 95% in the corresponding unpublished documents.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with unmatched studies, for which 43% of published studies contained adverse events information compared to 83% of unpublished studies.
We also found even when adverse events are reported in the published and unpublished versions of the same study that the numbers of adverse events do not always match The percentage of adverse events that would have been missed had each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Lastly we found that inclusion of unpublished data increased the precision of the pooled estimates (narrower 95% confidence intervals) in three-quarters of pooled analyses, but did not markedly change the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.
MedicalResearch.com: What should readers take away from your report?
Response: Research evidence on harmful effects of treatments should be reported fully and transparently, and made easily accessible without restriction. We call for urgent policy action to make all adverse events data readily accessible to the public in a full, unrestricted manner.
Authors of systematic reviews of adverse events should attempt to include unpublished data to gain a more complete picture of the adverse events, particularly in the case of rare adverse events.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: We need further research to find out if efforts to increase access to trial data (such as the AllTrials.net group) can enable more detailed and comprehensive safety evaluations, as compared to the current restricted situation. In particular, we need far more examples to see if availability of the unpublished data might lead us to arrive at different conclusions on safety.
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