Counting Antibiotics in Antibiotic Stewardship
Antibiotic stewardship programs should measure antibiotic use using Days of Therapy (DOTs) as the preferred metric over Defined Daily Doses (DDDs), with measurements stratified by individual antibiotic agent and normalized to patient census. 1
Primary Measurement Method: Days of Therapy (DOTs)
DOTs represent the gold standard for counting antibiotic use in stewardship programs. 1 This metric offers several critical advantages:
- DOTs are unaffected by dose adjustments, making them more accurate than DDDs for tracking actual antibiotic exposure 1
- DOTs can be applied to both adult and pediatric populations, whereas DDDs have significant limitations in pediatrics due to weight-based dosing 1
- The CDC's National Healthcare Safety Network requires DOT reporting through the Antimicrobial Use and Resistance Module, making this the standardized national metric 1
Alternative Method: Defined Daily Doses (DDDs)
DDDs remain an acceptable alternative for facilities that cannot obtain patient-level antibiotic use data, though they are less preferred. 1 This metric may be necessary when:
- Electronic health record systems cannot extract individual patient-level data 1
- Resource limitations prevent detailed tracking 1
- Facilities are transitioning to more sophisticated measurement systems 1
Implementation Requirements for Counting
Every antibiotic stewardship program must measure antibiotic use stratified by individual antibiotic agent. 1 The counting system should include:
- Normalization to patient census (e.g., DOTs per 1000 patient-days) to allow meaningful comparisons over time and between facilities 1
- Stratification by specific antibiotics rather than just total antibiotic use 1
- Unit-level, provider-level, or service-level breakdowns to identify targeted intervention opportunities 1
- Regular tracking and reporting to monitor trends and intervention effectiveness 2
Beyond Simple Counting: Appropriateness Measurement
Measuring antibiotic appropriateness through guideline compliance is equally important as counting volume. 1 Stewardship programs should:
- Assess compliance with facility-specific or national treatment guidelines, particularly when evaluating targeted interventions 1
- Share appropriateness data with clinicians to inform prescribing practices 1
- Monitor the "5 Ds of stewardship": right diagnosis, drug, dose, duration, and de-escalation 2
Cost Measurement Considerations
Antibiotic costs should be measured based on prescriptions or administrations rather than purchasing data. 1 This approach:
- Reflects actual patient-level use rather than pharmacy inventory changes 1
- Should be normalized to patient-days (e.g., antibiotic cost per patient-day) 1
- Must account for program costs including stewardship personnel salaries 1
- Should adjust for inflation when comparing across years 1
Secondary Outcome Metrics
While DOTs/DDDs represent the primary counting method, stewardship programs should track additional metrics cautiously:
- C. difficile infection rates have significant limitations as stewardship metrics because they are affected by infection control practices and other confounding factors 1
- Antibiotic resistance patterns are complex and influenced by multiple variables beyond antibiotic use alone 1
- These secondary outcomes may be useful for targeted interventions (e.g., CDI rates when reducing high-risk antibiotics like fluoroquinolones or cephalosporins) but should not be the primary measure of stewardship success 1
Common Pitfalls to Avoid
Do not rely solely on purchasing data for antibiotic counting, as this does not reflect actual patient exposure and can be misleading due to inventory fluctuations. 1
Do not implement counting systems without stratification by individual antibiotics, as aggregate data masks important prescribing patterns and prevents targeted interventions. 1
Do not use DDDs in pediatric populations when patient-level data is available, as weight-based dosing makes DDDs inaccurate in children. 1