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BMC Med Res Methodol. 2012; 12: 55.
Published online Apr 20, 2012. doi:  10.1186/1471-2288-12-55
PMCID: PMC3386863
The selection of search sources influences the findings of a systematic review of people’s views: a case study in public health
Claire Stansfield,corresponding author1 Josephine Kavanagh,1 Rebecca Rees,1 Alan Gomersall,2 and James Thomas1
1Evidence for Policy and Practice Information and Coordinating (EPPI-) Centre, Social Science Research Unit, Institute of Education, University of London, London, UK
2Centre for Evidence and Policy, King’s College London, London, UK
corresponding authorCorresponding author.
Claire Stansfield: c.stansfield/at/ioe.ac.uk; Josephine Kavanagh: j.kavanagh/at/ioe.ac.uk; Rebecca Rees: r.rees/at/ioe.ac.uk; Alan Gomersall: alan.gomersall/at/kcl.ac.uk; James Thomas: j.thomas/at/ioe.ac.uk
Received August 18, 2011; Accepted April 20, 2012.
Abstract
Background
For systematic reviews providing evidence for policy decisions in specific geographical regions, there is a need to minimise regional bias when seeking out relevant research studies. Studies on people’s views tend to be dispersed across a range of bibliographic databases and other search sources. It is recognised that a comprehensive literature search can provide unique evidence not found from a focused search; however, the geographical focus of databases as a potential source of bias on the findings of a research review is less clear. This case study describes search source selection for research about people’s views and how supplementary searches designed to redress geographical bias influenced the findings of a systematic review. Our research questions are: a) what was the impact of search methods employed to redress potential database selection bias on the overall findings of the review? and b) how did each search source contribute to the identification of all the research studies included in the review?
Methods
The contribution of 25 search sources in locating 28 studies included within a systematic review on UK children’s views of body size, shape and weight was analysed retrospectively. The impact of utilising seven search sources chosen to identify UK-based literature on the review’s findings was assessed.
Results
Over a sixth (5 out of 28) of the studies were located only through supplementary searches of three sources. These five studies were of a disproportionally high quality compared with the other studies in the review. The retrieval of these studies added direction, detail and strength to the overall findings of the review. All studies in the review were located within 21 search sources. Precision for 21 sources ranged from 0.21% to 1.64%.
Conclusions
For reducing geographical bias and increasing the coverage and context-specificity of systematic reviews of people’s perspectives and experiences, searching that is sensitive and aimed at reducing geographical bias in database sources is recommended.
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