The Agency for Healthcare Research and Quality (AHRQ), through its Evidence-based Practice Centers (EPCs), sponsors the development of systematic reviews to assist public- and private-sector organizations in their efforts to improve the quality of healthcare in the United States. The Health Resources and Services Administration requested this report from the EPC Program at AHRQ. AHRQ assigned this report to the following EPC: the Pacific Northwest Evidence-based Practice Center (Contract Number: 75Q80120D00006).

The reports and assessments provide organizations with comprehensive, evidence-based information on common medical conditions and new healthcare technologies and strategies. They also identify research gaps in the selected scientific area, identify methodological and scientific weaknesses, suggest research needs, and move the field forward through an unbiased, evidence-based assessment of the available literature. The EPCs systematically review the relevant scientific literature on topics assigned to them by AHRQ and conduct additional analyses when appropriate prior to developing their reports and assessments.

To bring the broadest range of experts into the development of evidence reports and health technology assessments, AHRQ encourages the EPCs to form partnerships and enter into collaborations with other medical and research organizations. The EPCs work with these partner organizations to ensure that the evidence reports and technology assessments they produce will become building blocks for healthcare quality improvement projects throughout the Nation. The reports undergo peer review and public comment prior to their release as a final report.

AHRQ expects that the EPC evidence reports and technology assessments, when appropriate, will inform individual health plans, providers, and purchasers as well as the healthcare system as a whole by providing important information to help improve healthcare quality.

If you have comments on this evidence report, they may be sent by mail to the Task Order Officer named below at: Agency for Healthcare Research and Quality, 5600 Fishers Lane, Rockville, MD 20857, or by email to vog.shh.qrha@cpe.

• Robert Otto Valdez, Ph.D., M.H.S.A
  Director
  Agency for Healthcare Research and Quality
• Craig A. Umscheid, M.D., M.S.
  Director
  Evidence-based Practice Center Program
  Center for Evidence and Practice Improvement
  Agency for Healthcare Research and Quality
• Arlene S. Bierman, M.D., M.S.
  Director
  Center for Evidence and Practice Improvement
  Agency for Healthcare Research and Quality
• Jill Huppert, M.D., M.P.H.
  Task Order Officer
  Center for Evidence and Practice Improvement
  Agency for Healthcare Research and Quality