How often is a Cochrane review the best available evidence? Analysis of the more relevant clinical questions

Article type
Authors
Rada G1
1Epistemonikos Foundation, Chile
Abstract
Background: Relying on Cochrane Reviews (CRs) is recognized as an efficient way of making evidence-based health decisions.
Objectives: To explore how often CRs are available for clinical questions; if they outperform other systematic reviews (SRs); and if they include all the relevant evidence.
Methods: In the context of a project aiming to create friendly summaries of evidence, we established groups composed of at least one content expert in 15 departments of the faculty of Medicine of the Pontificia Universidad Católica de Chile. Each team prioritized at least five questions about interventions that were considered hot topics in the area. We prepared matrices of evidence in Epistemonikos (a table comparing all of the reviews and all of the primary studies for a question).
We measured the number of available SRs for each question; the number of questions answered by a CR/non-Cochrane review (NCR); and the number of times a CR was the newer/more complete.
Results: Fifty-two clinical questions have been summarized at the moment. The average number of SRs per question was five (range 0 to 26). For 43/52 (83%) we identified at least one SR, but only 24/52 (46%) were answered by a CR. For the 24 questions for which a CR was available, in 16/24 (67%) the CR was the more complete, and in 12/24 (50%) it was the more recent. A total of 138/172 (80%) of the studies included in the CRs are included in other reviews. These results will be updated one month before the Colloquium.
Conclusion: A substantial proportion of questions can be answered with SRs. However, non-Cochrane reviews (NCRs) had better coverage than CRs. When there were both CRs and NCRs, CRs were more complete, but there is ample room for improvement. A large proportion of the included studies in a CR can be obtained from existing reviews. Our results emphasize the need for producing reviews covering the more relevant topics and the challenges for Cochrane to be the more reliable source of evidence. Using existing SRs might be an efficient way to filter the information overload and to position CRs as the best available evidence.