Missing data is a serious problem in clinical research given that it distorts the scientific record and prevents clinical decisions from being based on the best evidence available. As part of an in-depth BMJ review on the subject, experts on bmj.com warn that patients can be harmed through missing clinical trial data, leading to unnecessary costs to health systems.

BMJ has published several papers on the subject, assessing the causes, the extent, and consequences of unpublished evidence. The papers confirm that large proportions of evidence from human trials remain unreported, and that a lot of what is reported is inadequate.

Dr. Richard Lehman from the University of Oxford and BMJ Clinical Epidemiology Editor, Dr. Elizabeth Loder, talk of a “culture of haphazard publication and incomplete data disclosure,” in an editorial, calling for more vigorous regulation and full access to raw trial data to enable scientists to gain a better understanding of the benefits and harms of many kinds of treatment.

A study by Beth Hart and her team demonstrates that including unpublished data in published meta-analyses of drug trials has often altered the results of the analysis, debating that access to full trial data is necessary to allow an independent assessment of drugs.

The papers show that poor adherence to requirements for mandatory trial registration, and timely sharing of results has been demonstrated in two further studies; Whilst Ross and her team discovered that less than 50% of US National Institutes of Health funded trials are published within 30 months of completion in a peer reviewed journal, Andrew Prayle and his team established that only 22% of trials subject to mandatory reporting had their results available within one year of completion.

Lehman and Loder state:

“When the word ‘mandatory’ turns out to mandate so little, the need for stronger mechanisms of enforcement becomes very clear.”

Other studies published in the issue point out the numerous hurdles researchers need to overcome when trying to evaluate the true harms and benefits of common interventions.

According to Lehman and Loder the concealment of data is “a serious ethical breach” and clinical researchers who do not disclose data “should be subject to disciplinary action by professional organizations.”

They say in a concluding statement:

“These changes have long been called for, and delay has already caused harm. The evidence we publish shows that the current situation is a disservice to research participants, patients, health systems, and the whole endeavor of clinical medicine.”

A podcast on these issues is available here.

Writen by Petra Rattue