The comparative recall of Google Scholar versus PubMed in identical searches for biomedical systematic reviews: a review of searches used in systematic reviews

Abstract

BackgroundThe usefulness of Google Scholar (GS) as a bibliographic database for biomedical systematic review (SR) searching is a subject of current interest and debate in research circles. Recent research has suggested GS might even be used alone in SR searching. This assertion is challenged here by testing whether GS can locate all studies included in 21 previously published SRs. Second, it examines the recall of GS, taking into account the maximum number of items that can be viewed, and tests whether more complete searches created by an information specialist will improve recall compared to the searches used in the 21 published SRs.MethodsThe authors identified 21 biomedical SRs that had used GS and PubMed as information sources and reported their use of identical, reproducible search strategies in both databases. These search strategies were rerun in GS and PubMed, and analyzed as to their coverage and recall. Efforts were made to improve searches that underperformed in each database.ResultsGS’ overall coverage was higher than PubMed (98% versus 91%) and overall recall is higher in GS: 80% of the references included in the 21 SRs were returned by the original searches in GS versus 68% in PubMed. Only 72% of the included references could be used as they were listed among the first 1,000 hits (the maximum number shown). Practical precision (the number of included references retrieved in the first 1,000, divided by 1,000) was on average 1.9%, which is only slightly lower than in other published SRs. Improving searches with the lowest recall resulted in an increase in recall from 48% to 66% in GS and, in PubMed, from 60% to 85%.ConclusionsAlthough its coverage and precision are acceptable, GS, because of its incomplete recall, should not be used as a single source in SR searching. A specialized, curated medical database such as PubMed provides experienced searchers with tools and functionality that help improve recall, and numerous options in order to optimize precision. Searches for SRs should be performed by experienced searchers creating searches that maximize recall for as many databases as deemed necessary by the search expert.

Google Scholar Could Be Used as a Stand-Alone Resource for Systematic Reviews

“…A majority of these studies conclude that although GS can be used as one of several bibliographic databases for literature retrieval, researchers should not use it as a stand-alone tool (Bramer, Giustini, Kramer, & Anderson, 2013;Giustini & Kamel Boulos, 2013). The authors of this study conclude otherwise, indicating that GS is sensitive enough to use as a stand-alone resource when performing systematic reviews.…”

Improving the drug development process by reducing the impact of adverse events: the case of cataracts considered

“…The main literature database searched was Google Scholar over the period January 1990 to May 2015 for pre-clinical animal studies and over the period January 2005 to May 2015 for clinical studies in humans. It has elsewhere been shown that Google Scholar provides a high degree of coverage and precision with regards to similar literature search engines, such as PubMed/MED [4]. To find clinical trials, the search strategy involved using terms such as "phase I trial" cataract where trial was replaced with study and clinical and the phase was varied.…”

Taxonomy of Challenges in Medical Laboratory Diagnostic Services

“…Peer-reviewed literature as it is a common way to get access to the researchers" viewpoint whose selection is done using keywords based search. "Google Scholar" search engine is used for peer-reviewed papers as it is considered good and easy to operate source for public health related studies (Shariff et al 2013;Gehanno et al 2013;Shultz 2007) but, some cautions have been raised (Bramer et al 2013;Shultz 2007). The total of four levels of filtering mechanism is applied to shortlist journal papers for this study that lead to selection of 213 papers.…”