Using Embase as a supplement to PubMed in Cochrane reviews differed across fields.

OBJECTIVE: Medline/PubMed is often first choice for health science researchers when doing literature searches. However, Medline/PubMed does not cover the health science research literature equally well across specialties. Embase is often considered an important supplement to Medline/PubMed in health sciences. The present study analyzes the coverage of Embase as a supplement to PubMed, and the aim of the study is to investigate if searching Embase can compensate for low PubMed retrieval. STUDY DESIGN AND SETTING: The population in this study is all the included studies in all Cochrane reviews from 2012 to 2016 across the 53 Cochrane groups. The analyses were performed using two units of analysis (study and publication). We are examining the coverage in Embase of publications and studies not covered by PubMed (25,119 publications and 9,420 studies). RESULTS: The results showed that using Embase as a supplement to PubMed resulted in a coverage of 66,994 publications out of 86,167 and a coverage rate of 77.7, 95% CI [75.05, 80.45] of all the included publications. Embase combined with PubMed covered 48,326 out of 54,901 studies and thus had a coverage rate of 88.0%, 95% CI [86.2, 89.9] of studies. The results also showed that supplementing PubMed with Embase increased coverage of included publications by 6.8 percentage points, and the coverage of studies increased by 5.5 percentage points. Substantial differences were found across and within review groups over time. CONCLUSION: The included publications and studies in some groups are covered considerably better by supplementing with Embase, whereas in other groups, the difference in coverage is negligible. However, due to the variation over time, one should be careful predicting the benefit from supplementing PubMed with Embase to retrieve relevant publications to include in a review.

PubMed coverage varied across specialties and over time: a large-scale study of included studies in Cochrane reviews.

OBJECTIVE: PubMed is one of the most commonly used search tools in biomedical and life sciences. Existing studies of database coverage generally conclude that searching PubMed may not be sufficient although some find that the contributions from other databases are modest at best. However, generalizability of the studies of the coverage of PubMed is typically restricted. The objective of this study is to analyze the coverage of PubMed across specialties and over time. STUDY DESIGN AND SETTING: We use the more than 50,000 included studies in all Cochrane reviews published from 2012 to 2016 as our population and examine if the studies and resulting publications can be identified in PubMed. RESULTS: The results show that PubMed has a coverage of 70.9, 95% confidence interval (CI) (68.40, 73.30) of all the included publications and 82.8%, 95% CI (80.9, 84.7) of the included studies. There are huge differences in coverage across and within specialties. In addition, coverage varies within groups over time. CONCLUSION: Databases used for searching topics within the groups with highly varying or low coverage should be chosen with care as PubMed may have a relatively low coverage.