Days of Antibiotic Spectrum Coverage: A Novel Metric for Inpatient Antibiotic Consumption

Days of therapy (DOT), the most widely used benchmarking metric for antibiotic consumption, may not fully measure stewardship efforts to promote use of narrow-spectrum agents and may inadvertently discourage the use of combination regimens when single-agent alternatives have greater adverse effects. To overcome the limitations of DOT, we developed a novel metric, days of antibiotic spectrum coverage (DASC), and compared hospital performances using this novel metric with DOT.

We evaluated 77 antibiotics in 16 categories of antibacterial activity to develop our spectrum scoring system. DASC was then calculated as cumulative daily antibiotic spectrum coverage (ASC) scores. To compare hospital benchmarking using DOT and DASC, we conducted a retrospective cohort study of adult patients admitted to acute care units within the Veterans Health Administration system in 2018. Antibiotic administration data were aggregated to calculate each hospital's DOT and DASC per 1000 days present (DP) for ranking.

The ASC score for each antibiotic ranged from 2 to 15. There was little correlation between DOT per 1000 DP and DASC per DOT, indicating that lower antibiotic consumption at a hospital does not necessarily mean more frequent use of narrow-spectrum antibiotics. The differences in each hospital's ranking between DOT and DASC per 1000 DP ranged from -29.0% to 25.0%, respectively, with 27 hospitals (21.8%) having differences >10%.

We propose a novel composite metric for antibiotic stewardship, DASC, that combines consumption and spectrum as a potential replacement for DOT. Further studies are needed to evaluate whether benchmarking using the DASC will improve evaluations of stewardship.