Grading the Strength of a Body of Evidence When Assessing Health Care Interventions for the Effective Health Care Program of the Agency for Healthcare Research and Quality: An Update

Abstract

Systematic reviews are essential tools for summarizing information to help users make well-informed decisions about health care options. The Evidence-based Practice Center (EPC) program, supported by the Agency for Healthcare Research and Quality (AHRQ), produces substantial numbers of such reviews, including those that explicitly compare two or more clinical interventions (sometimes termed comparative effectiveness reviews). These reports synthesize a body of literature; the ultimate goal is to help clinicians, policymakers, and patients make well-considered decisions about health care. The goal of strength of evidence assessments is to provide clearly explained, well-reasoned judgments about reviewers’ confidence in their systematic review conclusions so that decisionmakers can use them effectively.Beginning in 2007, AHRQ supported a cross-EPC set of work groups to develop guidance on major elements of designing, conducting, and reporting systematic reviews. Together the materials form the EPC Methods Guide for Effectiveness and Comparative Effectiveness Reviews; one chapter focused on grading the strength of evidence. This chapter updates the original EPC strength of evidence approach, presenting findings and recommendations of a work group with experience in applying previous guidance; it should be considered current guidance for EPCs. The guidance applies primarily to systematic reviews of drugs, devices, and other preventive and therapeutic interventions; it may apply to exposures (characteristics or risk factors that are determinants of health outcomes) and broader health services research questions. It does not address reviews of medical tests.EPC reports support the work of many decisionmakers, but EPCs do not themselves develop recommendations or practice guidelines. In particular, we limit our grading strength of evidence approach to individual outcomes. Unlike grading systems that were designed to be used more directly by specific decisionmakers,– we do not develop global summary judgments of the relative benefits and harms of treatment comparisons.We briefly explore the rationale for grading strength of evidence, define domains of concern, and describe our recommended grading system for systematic reviews. The aims of this guidance are twofold: (1) to foster appropriate consistency and transparency in the methods that different EPCs use to grade strength of evidence and (2) to facilitate users’ interpretations of those grades for guideline development or other decisionmaking tasks. Because this field is rapidly evolving, future revisions are anticipated; they will reflect our increasing understanding and experience with the methodology.