Side effects are under-reported in peer reviewed journalsBMJ 2016; 354 doi: https://doi.org/10.1136/bmj.i5075 (Published 21 September 2016) Cite this as: BMJ 2016;354:i5075
Much of the information on adverse events remains unpublished, a systematic review of the evidence published in Plos Medicine has found.
Su Golder, from the University of York, and colleagues reviewed 28 studies that compared published journal articles with unpublished information on the same trials gathered from conference reports, drug companies’ clinical study reports, and other sources.1
The median percentage of published documents containing adverse event information was 46%, compared with 95% in the corresponding unpublished documents. Eleven of the 28 studies compared the numbers of named adverse events in matched published and unpublished documents. The overall percentage of adverse events that would have been missed had an analysis relied only on the published versions of studies varied between 43% and 100%, with a median of 64%. The review also found that a wider range of named side effects was reported in unpublished than in published studies.
The researchers wrote, “The extent of ‘hidden’ or ‘missing’ data prevents researchers, clinicians, and patients from gaining a full understanding of harm, and this may lead to incomplete or erroneous judgements on the perceived benefit to harm profile of an intervention.” They cited examples of systematic reviews that arrived at a very different conclusion after unpublished data were incorporated into the analysis, such as the Cochrane review on oseltamivir (Tamiflu).
The researchers called for authors of systematic reviews of adverse events to attempt to include unpublished data to gain a more complete picture of adverse events, particularly rare ones. They also called for urgent action to make all adverse events data readily accessible to the public in a full, unrestricted manner.