Google Scholar Versus PubMed in Locating Primary Literature to Answer Drug-Related Questions

BACKGROUND: Google Scholar linked more visitors to biomedical journal Web sites than did PubMed after the database's initial release; however, its usefulness in locating primary literature articles is unknown. OBJECTIVE: To assess in both databases the availability of primary literature target articles; total number of citations; availability of free, full-text journal articles; and number of primary literature target articles retrieved by year within the first 100 citations of the search results. METHODS: Drug information question reviews published in The Annals of Pharmacotherapy Drug Information Rounds column served as targets to determine the retrieval ability of Google Scholar and PubMed searches. Reviews printed in this column from January 2006 to June 2007 were eligible for study inclusion. Articles were chosen if at least 2 key words of the printed article were included in the PubMed Medical Subject Heading (MeSH) database, and these terms were searched in both databases. RESULTS: Twenty-two of 33 (67%) eligible Drug Information Rounds articles met the inclusion criteria. The median number of primary literature articles used in each of these articles was 6.5 (IQR 4.8, 8.3; mean +/- SD 8 +/- 5.4). No significant differences were found for the mean number of target primary literature articles located within the first 100 citations in Google Scholar and PubMed searches (5.1 +/- 3.9 vs 5.3 +/- 3.3; p = 0.868). Google Scholar searches located more total results than PubMed (2211.6 +/- 3999.5 vs 44.2 +/- 47.4; p = 0.019). The availability of free, full-text journal articles per Drug Information Rounds article was similar between the databases (1.8 +/- 1.7 vs 2.3 +/- 1.7; p = 0.325). More primary literature articles published prior to 2000 were located with Google Scholar searches compared with PubMed (62.8% vs 34.9%; p = 0.017); however, no statistically significant differences between the databases were observed for articles published after 2000 (66.4 vs 77.1; p = 0.074). CONCLUSIONS: No significant differences were identified in the number of target primary literature articles located between databases. PubMed searches yielded fewer total citations than Google Scholar results; however, PubMed appears to be more specific than Google Scholar for locating relevant primary literature articles.