Researchers: unpublished adverse reactions a 'serious problem'

By Melissa Fassbender contact

- Last updated on GMT

(Image: iStock/BrianAJackson)
(Image: iStock/BrianAJackson)

Related tags: Clinical trial

As the industry works to increase transparency in clinical trial data reporting, researchers have found that data on adverse effects remain largely unpublished.

We personally have faced these barriers of being unable to find the unpublished data on adverse effects, so we became concerned about lack of transparency and openness​,” Dr. Su Golder of University of York, UK, told

As such, Golder and his colleagues wanted to know if they were alone in facing “this serious problem, or if other researchers were also troubled by these difficulties in accessing data​,” he explained.

Subsequently, the researchers carried out a systematic review, results of which were recently published in PLOS Medicine.

The most surprising find was that such huge amounts of data are being collected in research, but not reported in journal articles​,” Golder said, who explained even fewer published papers contained adverse events information.

According to the review, the median percentage of published documents with adverse events information was 46% compared to 95% in the corresponding unpublished documents.

Golder explained 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with unmatched studies, for which 43% of published studies contained adverse events information compared to 83% of unpublished studies.

We also found even when adverse events are reported in the published and unpublished versions of the same study that the numbers of adverse events do not always match​,” he said.

Additionally, the percentage of adverse events that would have been missed if the analysis relied solely 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Lastly we found that inclusion of unpublished data increased the precision of the pooled estimates (narrower 95% confidence intervals) in three-quarters of pooled analyses, but did not markedly change the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​,” Golder said.

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,​” Golder and his colleagues concluded.

In a response to similar calls to action, the Obama administration recently finalized​ a new rule, which outlines requirements for registering clinical trials and submitting summary results information to

The new rule hopes to increase transparency in the industry and will mark a “change in a business in usual,​” according to​ the director of National Institutes of Health (NIH) Francis Collins.

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