A framework for best evidence approaches can improve the transparency of systematic reviews

Objective: Systematic reviewers often use a "best evidence" approach to address the key questions, but what is meant by "best" is often unclear. The goal of this project was to create a decision framework for "best evidence" approaches to increase transparency in systematic reviews. Study Design and Setting: The project was separated into three areas: 1) inclusion criteria, 2) evidence prioritization strategies, and 3) evaluative approaches. This commentary focuses only on the second task. The full report is available on the Effective Healthcare Web site of the Agency for Healthcare Research and Quality. Results: The four identified strategies were as follows: 1) Use only the single best study; 2) Use the best set of studies; 3) Same as 2, but also consider whether the evidence permits a conclusion; and 4) Same as 3, but also consider the overall strength of the evidence. Simpler strategies (such as #1) are less likely to produce false conclusions, but are also more likely to yield insufficient evidence (possibly because of imprecise data). Conclusion: Systematic reviewers routinely prioritize evidence in numerous ways. This document provides a conceptual construct to enhance the transparency of systematic reviewers' decisions.