Comparative effectiveness research: The translational science of comparing the what, how, when, in whom, by whom, and why of treatment effectiveness.

Recent health care legislation in the United States has turned considerable focus to comparative effectiveness research (CER) domestically, though it has been a topic of discussion internationally for many years. Without a fully comprehensive and consistent definition of CER developed, much uncertainty and confusion surrounds its utilization. In addition, contention exists regarding the incorporation of cost and economic considerations as a component of CER. This discussion includes various suggested definitions of CER, methodological considerations, legislation and utilization, and the role of cost-effectiveness evaluations in CER. [ABSTRACT FROM AUTHOR]