Abstract
BackgroundClinical trial registries can be used as sources of clinical evidence for systematic review synthesis and updating. Our aim was to evaluate methods for identifying clinical trial registrations that should be screened for inclusion in updates of published systematic reviews.MethodsA set of 4644 clinical trial registrations (ClinicalTrials.gov) included in 1089 systematic reviews (PubMed) were used to evaluate two methods (document similarity and hierarchical clustering) and representations (L2-normalised TF-IDF, Latent Dirichlet Allocation, and Doc2Vec) for ranking 163,501 completed clinical trials by relevance. Clinical trial registrations were ranked for each systematic review using seeding clinical trials, simulating how new relevant clinical trials could be automatically identified for an update. Performance was measured by the number of clinical trials that need to be screened to identify all relevant clinical trials.ResultsUsing the document similarity method with TF-IDF feature representation and Euclidean distance metric, all relevant clinical trials for half of the systematic reviews were identified after screening 99 trials (IQR 19 to 491). The best-performing hierarchical clustering was using Ward agglomerative clustering (with TF-IDF representation and Euclidean distance) and needed to screen 501 clinical trials (IQR 43 to 4363) to achieve the same result.ConclusionAn evaluation using a large set of mined links between published systematic reviews and clinical trial registrations showed that document similarity outperformed hierarchical clustering for identifying relevant clinical trials to include in systematic review updates.
Highlights
Clinical trial registries can be used as sources of clinical evidence for systematic review synthesis and updating
Systematic review Digital Object Identifier (DOI) identified on PubMed were used to query CrossRef to identify and extract reference lists associated with the systematic review article, where they were made available through the Initiative for Open Citations
These lists of DOIs representing the articles cited by the systematic review were searched for on PubMed, where the presence of an NCT National Clinical Trial Number (Number) in the article abstract or metadata was used to determine if there was a corresponding registration for a completed trial on ClinicalTrials.gov (Fig. 1)
Summary
Clinical trial registries can be used as sources of clinical evidence for systematic review synthesis and updating. Clinical study registries offer an opportunity to improve the efficiency of systematic review synthesis and updating but do not yet support informatics tools for this purpose. Trial registries have the potential to support systematic review processes by enabling a system to monitor ongoing trial activity and signal areas with higher rates of emerging evidence. This approach would depend on methods to accurately identify which clinical trial registrations were relevant to specific systematic review topics
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