Toolkit for Reduction of Clostridium difficile Infections Through Antimicrobial Stewardship

Ø RESOURCE 2C: Possible Methods for Evaluating Antibiotic Use

Purpose: A tool to review types of antibiotic use metrics.

Source: Developed by R. Ruiz, Greater New York Healthcare Association, for ERASE C. difficile Project toolkit.

Instructions: Use when considering ways to measure antibiotic use. Includes descriptions, strengths, consideration, types of stewardship interventions for which metrics have monitoring potential, and resources/references.

Metric Description Strengths Considerations Monitoring Potential References
Defined daily dose (DDD)* Average maintenance dose per day for a drug used for its main indication in adults. Gives an estimate of antibiotic consumption. DDD allows comparison of antibiotic consumption between groups/facilities.

Standardized DDD is independent of price and dose.

DDDs exist for common combination therapies.

Calculated DDDs account for dose and frequency given
DDD does not reflect the recommended or prescribed dose.

Most times the DDD is a compromise of doses used in different countries.

Standardized DDD is rarely the prescribed dose due to averaging of common doses used.

DDD can only be used for adults.

Calculation over time may be affected by changes in the standardized DDDs.
Antibiotic restriction.

Audit and feedback.

Computer triggers.

Clinical prompts (e.g., indication).
a, b
Days of therapy (DOT) Number of days when at least one dose of a medication was administered irrespective of dose or route of administration Allows comparison of the length of treatment.

Can be used for children.

Not dependent on standardized dose (like DDDs) for uncomplicated calculation over time.
Does not take into account dose or frequency Audit and feedback.

Clinical prompts (e.g., indication).
Number of courses Number of prescribed courses of unique antibiotics per person. Courses cannot have more than a 48-hour window between any two consecutive administrations. Allows comparison of antibiotic prescription patterns Does not take into account dose or frequency.

Does not take into account route of administration.
Antibiotic restriction.

Computer triggers.

Clinical prompts (e.g., indication).
≥Three antibiotics  Number of patients on three or more antibiotics Can be used to identify patients with more severe acuity and possibly at higher risk for complications (e.g., C. difficile). Does not take into account dose or frequency.

Does not take into account specific combinations of antibiotics.

May be prone to a small number of patients.
Audit and feedback  


a. World Health Organization Collaborating Centre for Drug Statistics Methodology. International language for drug utilization research. Oslo: Norwegian Institute of Public Health; 2012. Available at:

b. Polk RE, Fox C, Mahoney A, et al. Measurement of adult antibacterial drug use in 130 U.S. hospitals: comparison of defined daily dose and days of therapy. Clin Infect Dis 2007 Mar 1;44(5):664-70. Epub 2007 Jan 22.

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Page last reviewed September 2012
Internet Citation: Ø RESOURCE 2C: Possible Methods for Evaluating Antibiotic Use. September 2012. Agency for Healthcare Research and Quality, Rockville, MD.