Antimicrobial use metrics and benchmarking to improve stewardship outcomes: methodology, opportunities, and challenges.

Measurement of antimicrobial use before and after an intervention and the associated outcomes are key activities of antimicrobial stewardship programs. In the United States, the recommended metric for aggregate antibiotic use is days of therapy/1000 patient-days. Clinical outcomes, including response to therapy and bacterial resistance, are critical measures but are more difficult to document than economic outcomes. Interhospital benchmarking of risk adjusted antimicrobial use is possible, although several obstacles remain before it can have an impact on patient care. Many challenges for stewardship programs remain, but the methods and science to support their efforts are rapidly evolving.