Why observational studies should be among the tools used in comparative effectiveness research.

Doctors, patients, and other decision makers need access to the best available clinical evidence, which can come from systematic reviews, experimental trials, and observational research. Despite methodological challenges, high-quality observational studies have an important role in comparative effectiveness research because they can address issues that are otherwise difficult or impossible to study. In addition, many clinical and policy decisions do not require the very high levels of certainty provided by large, rigorous randomized trials. This paper provides insights and a framework to guide good decision making that involves the full range of high-quality comparative effectiveness research techniques, including observational research.