This study was supported by Contract 290-97-0011 from the Agency for Healthcare Research and Quality (AHRQ) (Task No. 7). We acknowledge the continuing support of Jacqueline Besteman, JD, MA, the AHRQ Task Order Officer for this project.

The investigators deeply appreciate the considerable support, commitment, and contributions from Research Triangle Institute staff Sheila White and Loraine Monroe.

In addition, we would like to extend our appreciation to the members of our Technical Expert Advisory Group (TEAG), who served as vital resources throughout our process. They are Lisa Bero, PhD, Co-Director of the San Francisco Cochrane Center, University of California at San Francisco, San Francisco, Calif.; Alan Garber, MD, PhD, Professor of Economics and Medicine, Stanford University, Palo Alto, Calif.; Steven Goodman, MD, MHS, PhD, Associate Professor, School of Medicine, Department of Oncology, Division of Biostatistics, Johns Hopkins University, Baltimore, Md.; Jeremy Grimshaw, MD, PhD, Health Services Research Unit, University of Aberdeen, Scotland; Alejandro Jadad, MD, DPhil, Director of the program in eHealth innovation, University Health Network, Faculty of Medicine, University of Toronto, Toronto, Canada; Joseph Lau, MD, Director, AHRQ Evidence-based Practice Center, New England Medical Center, Boston, Mass.; David Moher, MSc, Director, Thomas C. Chalmers Center for Systematic Reviews, Children's Hospital of Eastern Ontario Research Institute, Ontario, Canada; Cynthia Mulrow, MD, MSc, Founding Director of the San Antonio Evidence-based Practice Center, San Antonio, Texas, and Associate Editor, Annals of Internal Medicine; Andrew Oxman, MD, MSc, Director, Health Services Research Unit, National Institute of Public Health, Oslo, Norway; and Paul Shekelle, MD, MPH, PhD, Director, AHRQ Evidence-based Practice Center, RAND-Southern California, Santa Monica, Calif.

We owe our thanks as well to our external peer reviewers, who provided constructive feedback and insightful suggestions for improvement of our report. Peer reviewers were Alfred O. Berg, MD, MPH, Chairman, U.S. Preventive Services Task Force, and Professor and Chair, Department of Family Medicine, University of Washington, Seattle, Wash.; Deborah Shatin, PhD, Senior Researcher, United Health Group, Minnetonka, Minn.; Edward Perrin, PhD, University of Washington, Seattle, Wash.; Marie Michnich, DrPH, American College of Cardiology, Bethesda, Md.; Steven M. Teutsch, MD, MPH, Senior Director, Outcomes Research and Management, Merck & Co., Inc., West Point, Pa.; Thomas Croghan, MD, Eli Lilly, Indianapolis, Ind.; John W. Feightner, MD, MSc, FCFP, Chairman, Canadian Task Force on Preventive Health Care and St. Joseph's Health Centre for Health Care, London, Ontario, Canada; Steve Lascher, DVM, MPH, Clinical Epidemiologist and Research Manager in Scientific Policy and Education, American College of Physicians-American Society of Internal Medicine, Philadelphia, Pa.; Stephen H. Woolf, MD, MPH, Medical College of Virginia, Richmond, Va.; and Vincenza Snow, MD, Senior Medical Associate, American College of Physicians-American Society of Internal Medicine, Philadelphia, Pa. In addition, we would like to extend our thanks to the seven anonymous reviewers designated by AHRQ.

Finally, we are indebted as well to several senior members of the faculty at the University of North Carolina at Chapel Hill: Harry Guess, MD, PhD, of the Departments of Epidemiology and Statistics, and Vice President of Epidemiology at Merck Research Laboratories, Blue Bell, Pa.; Charles Poole, MPH, ScD, of the Department of Epidemiology; David Savitz, PhD, Chair, Department of Epidemiology; and Kenneth F. Schulz, PhD, MBA, School of Medicine and Vice President of Quantitative Methods, Family Health International, Research Triangle Park, N.C.