Web searching for systematic reviews: a case study of reporting standards in the UK Health Technology Assessment programme

Identifying literature for a systematic review requires searching a variety of sources. The main sources are typically bibliographic databases. Web searching using search engines and websites may be used to identify grey literature. Searches should be reported in order to ensure transparency and reproducibility. This study assesses the reporting of web searching for systematic reviews carried out by the National Institute for Health Research (NIHR) Health Technology Assessment (HTA) programme (UK). The study also makes recommendations about reporting web searching for systematic reviews in order to achieve a reasonable level of transparency and reproducibility. Systematic reviews were identified by searching the HTA database via the Centre for Reviews and Dissemination (CRD) website. Systematic reviews were included in the study if they made reference to searching the web using either search engines or websites. A data-extraction checklist was designed to record how web searching was reported. The checklist recorded whether a systematic review reported: the names of search engines or websites; the dates they were searched; the search terms; the results of the searches; and, in the case of websites, whether a URL was reported. 554 HTA reports published between January 2004 and December 2013 were identified. 300 of these reports are systematic reviews, of which 108 report web searching using either a search engine or a website. Overall, the systematic reviews assessed in the study exhibit a low standard of web search reporting. In the majority of cases, the only details reported are the names of websites (n = 54) or search engines (n = 33). A small minority (n = 6) exhibit the highest standard of web search reporting. Most web search reporting in systematic reviews carried out on the UK HTA programme is not detailed enough to ensure transparency and reproducibility. Transparency of reporting could be improved by adhering to a reporting standard such as the standard detailed in the CRD systematic reviews methods guidance. Reproducibility is harder to achieve due to the frequency of changes to websites and search engines.