Medical literature searches: a comparison of PubMed and Google Scholar

Background Medical literature searches provide critical information for clinicians. However, the best strategy for identifying relevant high-quality literature is unknown. Objectives We compared search results using PubMed and Google Scholar on four clinical questions and analysed these results with respect to article relevance and quality. Methods Abstracts from the first 20 citations for each search were classified into three relevance categories. We used the weighted kappa statistic to analyse reviewer agreement and nonparametric rank tests to compare the number of citations for each article and the corresponding journals' impact factors. Results Reviewers ranked 67.6% of PubMed articles and 80% of Google Scholar articles as at least possibly relevant (P similar to=similar to 0.116) with high agreement (all kappa P-values similar to