Using the antibiotic spectrum score to quantify the impact of hospital antimicrobial stewardship programmes

Background Antimicrobial stewardship (AMS) aims to de-escalate antibiotics from broad to narrow spectrum but there is a lack of evidence to support selection of patients who would most benefit from AMS review. Objectives We aimed to compare the days of antibiotic spectrum coverage (DASC) score with a standard AMS metric (days of therapy, DOT), to evaluate DASC as a tool to measure AMS impact. Methods Multi-centre retrospective cohort study of medical and surgical patients in two London hospitals. DASC and DOT were calculated for each prescription before and after AMS intervention and change in DOT and DASC calculated. We assessed correlation between DOT and DASC scores and associations between patient factors and reduction in post-AMS DOT or DASC. Results We evaluated 1287 prescriptions in 789 patients. AMS-associated change in DOT and DASC were correlated, but there was still substantial discordance between changes in DASC and changes in DOT, indicating that DASC may yield greater resolution on the impact of AMS review than DOT. Patients’ cumulative antibiotic spectrum score from all antibiotic prescriptions prior to AMS review correlated with the ensuing changes in DASC but not with changes in DOT. Conclusions Our findings support further assessment of the standardised antibiotic spectrum metric, DASC, for use in hospital AMS programmes to minimise adverse consequences of broad-spectrum antibiotic prescribing. Implementation of antibiotic spectrum measures have the potential to more accurately quantify the beneficial impact of inpatient AMS reviews, and assist in prioritising patients that most benefit from AMS-led interventions.