Grey literature in medicine has some valuable insight, according to a new paper. The authors say that clinical trial outcomes are more complete in unpublished reports than in publicly available information.

The results found that publicly available information contained less information about both the benefits and potential harms of an intervention than unpublished data. These findings highlight the importance of recent initiatives, such as the AllTrials initiative, that aim to make clinical trial outcome data publicly available, in order to provide complete and transparent information to help patients and clinicians reach decisions about clinical care.

In this paper, the researchers compared the information available in clinical study reports, which are detailed but usually unpublished accounts of clinical trials, to publicly available sources, including journal publications and registry reports.  They used a sample of 101 trials with full clinical study reports (CSRs) received for 16 HTAs of drugs completed by The Institute for Quality and Efficiency in Health Care (IQWiG) between 15 January 2006 and 14 February 2011, and analyzed the CSRs and the publicly available sources of these trials.

They found that that unpublished reports included complete information for 86% of the patient-relevant outcomes, whereas the combined publicly available sources provided complete information for only 39% of the outcomes. 

Pattern of reporting of trial outcomes in journal publications and/or registry reports. 
doi:10.1371/journal.pmed.1001526

Although the trials included in this study may not be representative of all trials, the findings support a draft policy released in June 2013 by the European Medicines Agency calling for the routine publication of complete clinical trial data.

The authors say, "Our findings show that a substantial amount of information on patient-relevant outcomes required for unbiased trial evaluation is missing from the public record."

They continue: "[Clinical study reports] should be made publicly available as they may substantially influence conclusions concerning the actual position of an individual drug in a therapeutic area."

"In line with our point of view, a further initiative to promote trial registration and reporting of full methods and results, the AllTrials initiative, also specifically refers to 'past and present' clinical trials."

Citation: Beate Wieseler, Natalia Wolfram,  Natalie McGauran,  Michaela F. Kerekes,  Volker Vervölgyi,  Petra Kohlepp, Marloes Kamphuis,   Ulrich Grouven, 'Completeness of Reporting of Patient-Relevant Clinical Trial Outcomes: Comparison of Unpublished Clinical Study Reports with Publicly Available Data. PLoS Med 10(10): e1001526. doi:10.1371/journal.pmed.1001526