Unpublished studies

Scope: use to index descriptions of this information type, collections of unpublished information, how to identify unpublished studies or investigations of the contribution of unpublished material as an information type. Use where the tag ‘grey literature’ does not reflect or capture this information type because it is genuinely unpublished, perhaps because it is referred to by a third party or represents a conference presentation without an accessible abstract

Appraisal of: “Korevaar DA, Hooft L, Askie LM, Barbour V, Faure H, Gatsonis CA, et al. Facilitating Prospective Registration of Diagnostic Accuracy Studies: A STARD Initiative. Clin Chem. 2017;63: 1331–1341.”

Short description: 

This paper provides the arguments for prospective registration of diagnostic test accuracy (DTA) studies in public databases. The authors do not advocate the creation of a specific registry for DTA studies, but registration is recommended in any available known public registry.  A list of possible registries is provided in Table 1 of the paper.

The authors propose a modified version of the WHO trial registration data set (Table 2 in the paper) which specifies the fields that would be needed for registry records to capture the key elements of a DTA study. 

Using their modified version of the WHO trial registration data set, the authors evaluated the reported information for the 30 most recently registered DTA studies in the WHO ICTRP in November 2016.  This small analysis provides some information for searchers who are searching for DTA studies in ICTRP.   In the sample of thirty studies, 90% reported that the study was a DTA study in the title of the record, 97% reported the target condition and 100% reported the index test.

The authors call on trial registries to ensure informative data are included in registry records to enhance identification.  They also call on journal editors to encourage DTA study registration prior to publication.

Limitations stated by the author(s): 

This is a position paper and it does not dwell upon limitations of its methods.

Limitations stated by the reviewer(s): 
The information for searchers is largely from the analysis of a small sample of thirty recent study records in ICTRP, but this information is highly valuable in indicating which aspects of DTA studies might be identifiable and retrievable within that database.

Appraisal of: Wieseler B, Wolfram N, McGauran N et al. Completeness of reporting of patient-relevant clinical trial outcomes: comparison of unpublished clinical study reports with publicly available data. PLoS Med 2013;10(10):e1001526.

Reviewer(s): 
Short description: 
The authors compared the information available in clinical study reports and in publicly accessible sources (journal articles, registry reports) included in 16 HTA reports for drugs prepared in IQWiG. They assessed the completeness of information on patient-relevant benefit (e.g. symptom relief, health related quality of life) and harm (adverse effects) outcomes reported in each document type. Clinical study reports provided complete information of all outcomes on a higher proportion (86%) than publicly accessible sources (39%). They also provided more information on harms (87% versus 43 %). The authors conclude that clinical study reports should be made publicly available for the benefit of unbiased trial evaluation and informed decision-making in health care.
Limitations stated by the author(s): 
The main limitation was that the authors could only study those clinical study reports that were provided voluntarily upon request by the pharmaceutical companies. Also, the sample of clinical study reports was restricted on studies investigating drugs.
Limitations stated by the reviewer(s): 
No additional limitations detected by the reviewer.
Study Type: 
Single study
Related Chapters: 

Appraisal of: Golder S, Loke YK. Sources of information on adverse effects. Health Info Libr J 2010;27:176-190.

Short description: 
Research has shown that most systematic reviews of adverse effects rely solely on searches of MEDLINE, even though it is unlikely to be a comprehensive source on adverse effects information. The authors aimed to identify and summarize studies that had evaluated sources of information on adverse effects. No date or language restrictions were applied when searching for studies. The results indicated that Embase, Derwent Drug File, MEDLINE and industry submissions might be the sources of the largest number of relevant references for adverse effects information. In addition, they concluded that searching a wide range of sources might be a useful approach when conducting a thorough search.
Limitations stated by the author(s): 
Studies included in the review were inconsistent in their use of outcome measures. They used different information sources which made direct comparisons difficult. Recent research information was lacking and many of the studies were more than 10 years old. Many potentially useful information sources were not covered in the studies identified (e.g. search engines and industry clinical trial registers). Most studies reported only the number of relevant references retrieved for comparison which is not a sufficient criterion. Also, the cost of searching different sources had not been assessed.
Limitations stated by the reviewer(s): 
No additional limitations detected by the reviewer.
Study Type: 
Review
Related Chapters: 
Comments from the authors:
 
This publication is related to Su Golder’s PhD Thesis “Evaluating and Optimising the Retrieval of Research Evidence for Systematic Reviews of Adverse Drug Effects and Adverse Drug Reactions” from 2013. The thesis is available from http://etheses.whiterose.ac.uk/4749/

Appraisal of: Golder S, Loke YK, Bland M. Unpublished data can be of value in systematic reviews of adverse effects: methodological overview. J Clin Epidemiol 2010;63(10):1071-1081.

Short description: 
The authors assessed the impact of including unpublished data on adverse effects in systematic reviews. They carried out a systematic review of methodological evaluations comparing the quantitative reporting of adverse effects data between published and unpublished sources. The key finding was that unpublished studies could provide additional adverse effects information. However, there was insufficient data to conclude whether including unpublished studies would have major impact on the results of meta-analyses.
Limitations stated by the author(s): 
Methodological evaluations are difficult to retrieve by database searches and it is possible that review articles may have been missed. There is also a possibility of reporting or publication bias with respect to methodological evaluations, as investigators may have chosen not to report their findings if they did not find any significant differences between published and unpublished studies.
Limitations stated by the reviewer(s): 
No additional limitations detected by the reviewer.
Study Type: 
Review
Related Chapters: 

Comments from the authors:

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