Prepared for:

Agency for Health Care Research and Quality

U.S. Department of Health and Human Services

540 Gaither Road

Rockville, MD 20850

www.ahrq.gov

Contract No. 290-02-0024, Task Order Number 2

Prepared by:

Oregon Evidence-based Practice Center

Center for Health Research

3800 North Interstate Avenue

Portland, OR 97227

Investigators:

Selvi Williams, MD, MPH

Evelyn Whitlock, MD, MPH

Paula Smith, RN, BSN,

Beth Edgerton, MD, MPH

Tracy Beil, MS

AHRQ Publication No. 07-05103-EF-1

August 2007

This report is based on research conducted by the Oregon Evidence-based Practice Center (EPC) under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, MD (Contract No. 290-02-0024).

The findings and conclusions in this document are those of the author(s), who are responsible for its content, and do not necessarily represent the views of AHRQ. 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 clinicians, employers, policymakers, and others make informed decisions about the provision of health care services. This report is intended as a reference and not as a substitute for clinical judgment.

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