Prepared for:

Agency for Healthcare Research and Quality

U.S. Department of Health and Human Services

http://www.ahrq.gov

Contract No. 290-97-0014

Prepared by:

Duke Evidence-based Practice Center

Douglas C. McCrory, MD, MHSc

John W. Williams, MD

Rowena J. Dolor, MD, MHS

Rebecca N. Gray, DPhil

Jane T. Kolimaga, MA

Shelby Reed, PhD

John Sundy, MD, PhD

David L. Witsell, MD

Investigators

AHRQ Publication No. 03-E015

March 2003

ISBN: 1-58763-077-X

ISSN: 1530-4396

This report may be used, in whole or in part, as the basis for development of clinical practice guidelines and other quality enhancement tools, or as a basis for reimbursement and coverage policies. Endorsement by the Agency for Healthcare Research and Quality (AHRQ) or the U.S. Department of Health and Human Services (DHHS) of such derivative products may not be stated or implied.

AHRQ is the lead Federal agency charged with supporting research designed to improve the quality of health care, reduce its cost, address patient safety and medical errors, and broaden access to essential services. AHRQ sponsors and conducts research that provides evidence-based information on health care outcomes; quality; and cost, use, and access. The information helps heath care decisionmakerspatients and clinicians, health system leaders, and policymakersmake more informed decisions and improve the quality of health care services.