Guidelines are systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical conditions. This guideline update was developed by a private-sector panel convened by the Agency for Health Care Policy and Research (AHCPR). The panel employed an explicit, science-based methodology and expert clinical judgment to develop specific statements on patient assessment and management for the clinical condition selected.

Extensive literature searches were conducted and critical reviews and syntheses were used to evaluate empirical evidence and significant outcomes. Peer review and field review were undertaken to evaluate the validity, reliability, and utility of the guideline in clinical practice. The panel's recommendations are primarily based on the published scientific literature. When the scientific literature was incomplete or inconsistent in a particular area, the recommendations reflect the professional judgment of panel members and consultants.

Guideline updates are a result of periodic review of the state of scientific information and technology. Updates reflect new research findings, experience, or technologies and provide specific recommendations in the field.

We believe that the AHCPR-assisted clinical practice guidelines will make positive contributions to the quality of care in the United States. We encourage practitioners and patients to use the information provided in this Clinical Practice Guideline Update. The recommendations may not be appropriate for use in all circumstances. Decisions to adopt any particular recommendation must be made by the practitioner in light of available resources and circumstances presented by individual patients.

• Clifton R. Gaus, ScD
• Administrator
• Agency for Health Care Policy and Research

Publication of this guideline does not necessarily represent endorsement by the U.S. Department of Health and Human Services.