Days of antibiotic spectrum coverage (days of ASC: DASC) is a metric for antibiotic usage calculated by ASC scores for spectrum and addresses limitations of days of therapy (DOT), which does not include spectrum. This study aims to investigate whether ASC-related metrics offer different aspects compared to aggregated DOT for all antibiotics (DOTtotal) and to assess their correlation in evaluating the impact of antimicrobial stewardship team (AST) programs.

Retrospective.

A single center within an 845-bed hospital.

Trends in DOTtotal, DASC, and the DASC/DOT ratio, representing the average spectrum coverage per therapy day, were analyzed pre- and post-AST programs (April 2018) from January 2015 to December 2023, using interrupted time series analysis. Independent of the DASC/DOT, we also advocated ASC-stratified DOT (ASDOT), which facilitates comprehensive evaluation of DOT across ASC scores of <6, 6–10, and >10, representing narrow-, intermediate-, and broad-spectrum antibiotics.

Among inpatients, AST programs significantly moderated the increasing trends of these metrics. Specifically, although the rates of increase in DOTtotal and DASC were slowed or plateaued, the DASC/DOT ratio decreased (P < 0.001). ASDOT metrics revealed a decrease and subsequent plateau in DOTtotal for the broad- and intermediate-spectrum antibiotics, with an increase observed for the narrow-spectrum antibiotics (P < 0.001 for each). DASC did not provide additional insights in the outpatient’s population.

The study demonstrates that ASC-related metrics may yield different and useful conclusions about the effectiveness of AST programs for inpatients.