Searching ClinicalTrials.gov and the International Clinical Trials Registry Platform to inform systematic reviews: what are the optimal search approaches?
Abstract:For systematic reviews, trials registers and major bibliographic databases should be searched. Trials registers should be searched using sensitive approaches, and both the registers consulted in this study should be searched.
“…Eysenbach et al [20] provide an approach to internet searching for unpublished clinical trials. There are published studies on searching specific resources systematically, for example, Google Scholar [21–24] and trials registers [25]. Outside of the systematic review literature, Blakeman [26] outlines challenges and approaches for searching Google effectively and discusses other online resources and tools for retrieving research.…”
Section: Introductionmentioning
confidence: 99%
“…Glanville et al [25] studied search approaches for two clinical trials registries, ICTRP and Clinicaltrials.gov, and found single-concept searches in the basic interfaces to be the most reliable. Haddaway et al [24] investigated approaches for searching Google Scholar, which only displays the first 1000 references of a search; they found that title searches enabled discovery of more grey literature (conference proceedings, theses, reports) than full-text searches.…”
Websites and online resources outside academic bibliographic databases can be significant sources for identifying literature, though there are challenges in searching and managing the results. These are pertinent to systematic reviews that are underpinned by principles of transparency, accountability and reproducibility. We consider how the conduct of searching these resources can be compatible with the principles of a systematic search. We present an approach to address some of the challenges. This is particularly relevant when websites are relied upon to identify important literature for a review. We recommend considering the process as three stages and having a considered rationale and sufficient recordkeeping at each stage that balances transparency with practicality of purpose. Advances in technology and recommendations for website providers are briefly discussed.
“…Eysenbach et al [20] provide an approach to internet searching for unpublished clinical trials. There are published studies on searching specific resources systematically, for example, Google Scholar [21–24] and trials registers [25]. Outside of the systematic review literature, Blakeman [26] outlines challenges and approaches for searching Google effectively and discusses other online resources and tools for retrieving research.…”
Section: Introductionmentioning
confidence: 99%
“…Glanville et al [25] studied search approaches for two clinical trials registries, ICTRP and Clinicaltrials.gov, and found single-concept searches in the basic interfaces to be the most reliable. Haddaway et al [24] investigated approaches for searching Google Scholar, which only displays the first 1000 references of a search; they found that title searches enabled discovery of more grey literature (conference proceedings, theses, reports) than full-text searches.…”
Websites and online resources outside academic bibliographic databases can be significant sources for identifying literature, though there are challenges in searching and managing the results. These are pertinent to systematic reviews that are underpinned by principles of transparency, accountability and reproducibility. We consider how the conduct of searching these resources can be compatible with the principles of a systematic search. We present an approach to address some of the challenges. This is particularly relevant when websites are relied upon to identify important literature for a review. We recommend considering the process as three stages and having a considered rationale and sufficient recordkeeping at each stage that balances transparency with practicality of purpose. Advances in technology and recommendations for website providers are briefly discussed.
“…Trial registration numbers (TRNs) may assist identification of a protocol for a known trial but do nothing to assist retrieval of previously unknown trials that match the inclusion criteria for a systematic review. The plethora of terms and synonyms required to achieve sensitive retrieval of such trials from a trial register may prove prohibitive given registers' limited functionality when compared with bibliographic databases . Empirical studies are required to establish (i) what proportion of trial protocols are retrievable by using pragmatic methods of retrieval, (ii) what the most effective methods for retrieving protocols are, (iii) what the main barriers in retrieving protocols are, and (iv) whether the most easily retrieved copy of the protocol remains the document of record.…”
For protocols of trial results published pre-2005, review authors should contact authors as a priority. For protocols post-2005, they should check the trial publication for protocol details, search trial registers, and contact authors, ceasing searching once a predetermined point of diminishing returns has been reached.
“…The choice of which concept to use in each register is likely to differ. Glanville recommends, for example, that when searching the ICTRP, searches using more than 1 concept should be constructed with caution because the Boolean operators are processed in a specific order within the interface and nesting is not supported. Effective searches of the ICTRP require repetitive use of terms, for example repeating the disease with each intervention as shown in the following example of nails for tibial fractures: tibia* AND nail* OR tibia* AND pin* OR tibia* AND screw* OR tibia* AND plate* OR tibia* AND fix* OR tibia* AND prosthe* OR tibia* AND ream* OR tibia* AND unream*…”
Section: Searching Trials Registers and Other Resourcesmentioning
Clinical trial data are essential for assessments of the effectiveness of health care interventions. Information about ongoing or completed, but not yet formally published, trials has been more difficult to identify until the development of clinical trials registers and portals. This paper summarises research evidence on identifying sources of trial data, how and when to search those sources, and which future developments may enhance access to and retrieval of unpublished trial evidence. We conducted a literature search for relevant studies and provide a narrative review of the evidence from these studies. Clinical trial data can be found in resources including clinical trials registers, regulatory agency sources, health technology assessment websites and manufacturers' websites, and submissions for regulatory approval. The challenges of searching these resources are described. Trials registers are relatively unsophisticated in terms of their search interfaces, and searchers need to adapt to each individual register. There is overlap across registers, but little research on the degree and nature of overlap and how best to search. Despite these challenges, trials registers and other resources can be rich sources of additional unique trial data, which may not be available from journal reports. New initiatives, such as OpenTrials, aim to consolidate and link all structured data and documentation related to clinical trials. No single resource gives access to all trials, and multiple registers should be searched as sensitively as possible. Searching is challenging and should be adequately resourced. Information specialists should monitor new developments which may reduce the challenges over the coming years.
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