Fellow Monroe Carell Jr. Children's Hospital at Vanderbilt Nashville, Tennessee, United States
Background: The Antibiotic Spectrum Index (ASI) is a recently developed quantitative measure of antibiotic utilization (per antibiotic score range: 1-13 based on spectrum of antimicrobial activity) that may be useful in the context of stewardship-focused interventions. Objective: We evaluated ASI as a pragmatic outcome measure in the context of a recent stewardship-focused, clinical trial. Design/Methods: The Improving Care for Community-Acquired Pneumonia (ICECAP) pragmatic trial compared antibiotic clinical decision support (CDS) vs usual care within the context of routine clinical care, enrolling encounters for children (6 months to 18 years) presenting to the emergency department (ED) with pneumonia at two US children’s hospitals (Dec. 2018- Sep. 2020). Encounters were randomized to CDS or usual care alone in 4-week periods within each site. The CDS intervention provided antibiotic recommendations in alignment with national guidelines. The trial’s primary outcome was guideline-concordant prescribing, a dichotomous measure. For this analysis, we evaluated ASI as a pragmatic stewardship outcome within the ICECAP population. For each encounter, ASI was defined as the sum of ASI scores for each antibiotic administered during the first 24 hours of care. ASI was evaluated overall and as an ordered outcome defined as ASI 0-2 (narrow spectrum), ASI 3-5, ASI 6-9, and ASI ≥10 (broadest spectrum) (Table 1). Proportional odds regression was used to model ASI categories by treatment arm. Results were also stratified by ED disposition (outpatient, inpatient, ICU) and among children receiving antibiotics. Results: 1027 encounters were included, with 549 randomized to CDS and 478 to usual care. Median ASI was 4 (IQR 2,7). Median ASI differed by ED disposition, (median [interquartile range]: outpatient 2 [0,4]; inpatient 5 [2,9]; intensive care 9 [5,9]). In the inpatient setting, less than one-third of encounters were in the most narrow ASI category. In the ICU, nearly half were in the broadest ASI category (Figure 1). Consistent with the trial’s primary outcome, ASI did not differ by treatment arm, although CDS appeared more effective among outpatients discharged from the ED (Table 2).
Conclusion(s): The ASI yielded similar results to the trial’s dichotomous concordance outcome. The ASI also allows for the classification of a variety of empiric treatment strategies into a single outcome based on antimicrobial spectrum, providing additional useful explanatory detail in the context of a stewardship-focused, pragmatic clinical trial.