Comparison of Medline and Embase retrieval of RCTs of the effects of educational interventions on asthma-related outcomes

Wolf, Fred and Grum, Cyril and Bara, Anna and Milan, Stephen James and Jones, Paul (1995) Comparison of Medline and Embase retrieval of RCTs of the effects of educational interventions on asthma-related outcomes. In: UNSPECIFIED.

Abstract

Introduction: Medline (Index Medicus) includes approximately 3700 journals, mostly but not entirely in the English language. Embase (Excerpta Medica) includes approximately 3500 journals, including many non-English language journals. Thus it is logical to hypothesize that the comprehensiveness of any systematic review may be enhanced by thoroughly searching both databases, rather than just one or the other. The degree to which this is true is not presently clear. Objective: To ascertain the degree of overlap and the unique contributions of Medline and Embase in identifying randomized controlled trials (RCTs) of the effectiveness of educational interventions in improving asthma-related outcomes. Methods: Electronic searches of the Medline (1966 - April 1995) and Embase (1980-April 1995) databases were conducted, based on the standard Cochrane Collaboration search strategy for RCTs (1994 Cochrane Collaboration Handbook, Chapter V) in combination with "and asthma" and "and education". Results: A total of 205 citations were retrieved. Of these 205 citations, 144 were in Medline and 105 in Embase, constituting 70.7% and 51.2% hit ratios, respectively. There were a total of 44 duplicate records (21.5% of the entire 205). Medline contributed 100 (or 48.8%) of the unique records, while Embase contributed 61 (or 29.8%). Discussion: While there is some overlap in the retrieval of citations from electronic searches of Medline and Embase, anywhere from 29-48% of the potential RCTs on the effectiveness of educational interventions on asthma-related outcomes reported between 1966-April 1995 would have been missed had the search been limited to either one of the two databases. While it is likely that not all of these citations are true RCTs, past experience suggests that hand searching of relevant journals would yield additional true RCTs that were not indexed as such in either database. Reasons for the uniqueness in retrieval of the two databases may be a function of coverage of different journals and how they are indexed, the fact that Medline goes back further in time, as well as other factors.