Search strategies to identify observational studies in MEDLINE and Embase

• Published in: Cochrane database of systematic reviews 2019-03, Vol.3 (3), p.MR000041
• Main Authors: Li, Li, Smith, Helen E, Atun, Rifat, Tudor Car, Lorainne
• Format: Article
• Language: English
• Subjects: Abstracting and Indexing - standards; Databases, Bibliographic; Information Storage and Retrieval - methods; MEDLINE; Methodology; Non-Randomized Controlled Trials as Topic; Observational Studies as Topic; Sensitivity and Specificity; STUDY IDENTIFICATION; Systematic Reviews as Topic
• ISSN: 1469-493X; 1469-493X
• DOI: 10.1002/14651858.MR000041.pub2

Systematic reviews are essential for decision-making. Systematic reviews on observational studies help answer research questions on aetiology, risk, prognosis, and frequency of rare outcomes or complications. However, identifying observational studies as part of systematic reviews efficiently is challenging due to poor and inconsistent indexing in literature databases. Search strategies that include a methodological filter focusing on study design of observational studies might be useful for improving the precision of the search performance. To assess the sensitivity and precision of a search strategy with a methodological filter to identify observational studies in MEDLINE and Embase. We searched MEDLINE (1946 to April 2018), Embase (1974 to April 2018), CINAHL (1937 to April 2018), the Cochrane Library (1992 to April 2018), Google Scholar and Open Grey in April 2018, and scanned reference lists of articles. Studies using a relative recall approach, i.e. comparing sensitivity or precision of a search strategy containing a methodological filter to identify observational studies in MEDLINE and Embase against a reference standard, or studies that compared two or more methodological filters. Two review authors independently screened articles, extracted relevant information and assessed the quality of the search strategies using the InterTASC Information Specialists' Sub-Group (ISSG) Search Filter Appraisal Checklist. We identified two eligible studies reporting 18 methodological filters. All methodological filters in these two studies were developed using terms from the reference standard records.The first study evaluated six filters for retrieving observational studies of surgical interventions. The study reported on six filters: one Precision Terms Filter (comprising terms with higher precision while maximum sensitivity was maintained) and one Specificity Terms Filter (comprising terms with higher specificity while maximum sensitivity was maintained), both of which were adapted for MEDLINE, for Embase, and for combined MEDLINE/Embase searches. The study reported one reference standard consisting of 217 articles from one systematic review of which 83.9% of the included studies were case seriesThe second study reported on 12 filters for retrieving comparative non-randomised studies (cNRSs) including cohort, case-control, and cross-sectional studies. This study reported on 12 filters using four different approaches: Fixed method A (comprising of a fixed set of