Selecting Observational Studies for Comparing Medical Interventions. Methods Guide for Comparative Effectiveness Reviews

摘要

While systematic reviewers disagree about the role of observational studies in answering questions about the benefits or intended effects of interventions, there is widespread agreement that observational studies, particularly those derived from large clinical and administrative databases, should be used routinely to identify and quantify potential adverse events. Existing systematic reviews vary significantly in the use of observational studies for questions of efficacy or effectiveness of interventions. This variation stems in part from concerns regarding the risk of bias in observational intervention studies, particularly the recognition that intended effects are more likely to be biased by preferential prescribing based on patients' prognosis. In addition, the inclusion of data from observational studies increases the time and resources required to complete a comparative effectiveness review (CER) which is already a time- and resource-intensive endeavor. Our objective is to provide a conceptual framework for the inclusion of observational studies in CERs examining beneficial or intended effects of pharmacotherapeutic, device, or procedural interventions. CERs expand the scope of a typical systematic review, which focuses on the efficacy or effectiveness of a single intervention, by comparing the relative benefits and harms among a range of available treatments or interventions for a given condition. In doing so, CERs more closely parallel the decisions facing clinicians, patients, and policymakers, who must choose among a variety of alternatives in making diagnostic, treatment, and health care delivery decisions.