Development and Application of an Antibiotic Spectrum Index (AbSI) for Benchmarking Antibiotic Selection Patterns Across Hospitals
Background: There are few established metrics for comparing antimicrobial use across hospitals. One commonly used metric is days of therapy (DOT) per 1000 patient days, but this does not measure differences in antibiotic selection patterns, an important influence on antibiotic resistance. We developed a scoring system, the antibiotic spectrum index (AbSI) that ranks antibiotic use based on spectrum of activity to facilitate inter-hospital comparisons in prescribing patterns.
Methods: We classified systemic antibiotics using a score ranking each agent based on spectrum of activity; for each agent the overall score could range from 0-14 points. One point was added to the score for activity against each of the following pathogens: MSSA, MRSA, E. faecalis, VRE, E. coli and Klebsiella, ampC producers, ESBL, Pseudomonas, penicillin-resistant pneumococcus (PRP), Moraxella and H. influenzae, Mycoplasma and Chlamydophila, and anaerobes. Drugs considered “last line” agents received an additional point. For example, the vancomycin AbSI = 5 (MSSA, MRSA, E. faecalis, PRP, last line). Data was obtained for 36 children's hospitals in 2012 from the Pediatric Health Information System and an aggregate spectrum score (sum of scores of all systemic antibiotics) was calculated for each day of antibiotic therapy for each patient. The standardized spectrum score per day of antibiotic therapy was compared across hospitals, adjusting for patient demographics and severity of illness and stratifying by condition using APR-DRG codes.
Results: Of the 5 conditions accounting for the most overall antibiotic days, AbSI identified low (5.7 and 6.7 for skin/soft tissue infection and pneumonia, respectively), medium (8.0 for appendectomy), and high (10.8 and 14.6 for bone marrow transplant and cystic fibrosis, respectively) index conditions. There was substantial variation in the total aggregate AbSI across hospitals within high use conditions (Figure).
Conclusion: Development and application of an antibiotic spectrum index can objectively classify commonly used agents based on activity against important pathogens. This score facilitates inter-hospital benchmarking and comparisons; follows expected patterns based on illness severity; and can be used to identify important clinical targets for antimicrobial stewardship.
T. A. Metjian,
M. Kronman, None
J. Newland, Pfizer: Grant Investigator, Grant recipient
R. Ross, None
J. S. Gerber, None