This report is based on research conducted by the RTI International–University of North
Carolina Evidence-based Practice Center (EPC) under contract to the Agency for Healthcare
Research and Quality (AHRQ), Rockville, MD (Contract No. 290-2007-10056-I). The findings
and conclusions in this doc ument are those of the authors, who are responsible for its contents;
the findings and conclusions do not necessarily represent the views of AHRQ. Therefore, no
statement in this report should be construed as an official position of AHRQ or of the U.S.
Department of Health and Human Services.
The information in this report is intended to help health care decisionmakers—patients and
clinicians, health system leaders, and policymakers, among others—make well-informed
decisions and thereby improve the quality of health care services. This report is not intended to
be a substitute for the application of clinical judgment. Anyone who makes decisions concerning
the provision of clinical care should consider this report in the same way as any medical
reference and in conjunction with all other pertinent information, i.e., in the context of available
resources and circumstances presented by individual patients.