Abstract
BackgroundHealth inequalities, worse health associated with social and economic disadvantage, are reported by a minority of research articles. Locating these studies when conducting an equity-focused systematic review is challenging due to a deficit in standardised terminology, indexing, and lack of validated search filters. Current reporting guidelines recommend not applying filters, meaning that increased resources are needed at the screening stage.MethodsWe aimed to design and test search filters to locate studies that reported outcomes by a social determinant of health. We developed and expanded a ‘specific terms strategy’ using keywords and subject headings compiled from recent systematic reviews that applied an equity filter. A ‘non-specific strategy’ was compiled from phrases used to describe equity analyses that were reported in titles and abstracts, and related subject headings. Gold standard evaluation and validation sets were compiled. The filters were developed in MEDLINE, adapted for Embase and tested in both. We set a target of 0.90 sensitivity (95% CI; 0.84, 0.94) in retrieving 150 gold standard validation papers. We noted the reduction in the number needed to screen in a proposed equity-focused systematic review and the proportion of equity-focused reviews we assessed in the project that applied an equity filter to their search strategy.ResultsThe specific terms strategy filtered out 93-95% of all records, and retrieved a validation set of articles with a sensitivity of 0.84 in MEDLINE (0.77, 0.89), and 0.87 (0.81, 0.92) in Embase. When combined (Boolean ‘OR’) with the non-specific strategy sensitivity was 0.92 (0.86, 0.96) in MEDLINE (Embase 0.94; 0.89, 0.97). The number needed to screen was reduced by 77% by applying the specific terms strategy, and by 59.7% (MEDLINE) and 63.5% (Embase) by applying the combined strategy. Eighty-one per cent of systematic reviews filtered studies by equity.ConclusionsA combined approach of using specific and non-specific terms is recommended if systematic reviewers wish to filter studies for reporting outcomes by social determinants. Future research should concentrate on the indexing standardisation for equity studies and further development and testing of both specific and non-specific terms for accurate study retrieval.
Highlights
Health inequalities, worse health associated with social and economic disadvantage, are reported by a minority of research articles
A comprehensive strategy comprised of specific terms related to the social determinants of health filtered out 93-95% of all records, and had a sensitivity of 0.84 in MEDLINE, and 0.87 in Embase against a gold standard set of records
The number needed to screen for the motivating systematic review was reduced by 77% by applying the specific terms strategy, and by 59.7% (MEDLINE) to 63.5% (Embase) by applying the combined strategy
Summary
Worse health associated with social and economic disadvantage, are reported by a minority of research articles. We label the notion of unfair and avoidable differences in health by socioeconomic group as ‘equity’ throughout this paper, noting that the terms health inequalities, inequities, and disparities are increasingly used interchangeably [2] Locating this minority of studies within the literature is a challenge that is hampered by the absence of validated equity search filters [3]. The current Preferred Reporting Items for Systematic Reviews and Meta-Analyses equity extension guidance (PRISMA-E) recommends that systematic reviewers do not attempt to filter searches due to poor indexing of equity terms which would lead to relevant studies being missed [4]. It is unclear how many systematic reviewers follow this advice. An obvious disadvantage to the advised sensitive (non-filtered) approach to study identification is that increased resources are needed at the screening stage, which can place a considerable burden on the research team [5]
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