Using Days of Antibiotic Spectrum Coverage to Quantify Antibiotic De-escalation: A Single-center Observational Study

Background/Aim: Effective monitoring of antibiotic use is essential for antimicrobial stewardship. While Days of Therapy (DOT) is commonly used to assess antibiotic consumption, it does not fully capture changes in antimicrobial spectrum during de-escalation. To address this, the Days of Antibiotic Spectrum Coverage (DASC) metric–calculated using a spectrum score weighted by antimicrobial breadth–was developed. This study aimed to evaluate the utility of DASC in identifying trends in antibiotic de-escalation across hospital wards and to determine whether it can serve as a reliable metric for assessing the appropriateness of antibiotic use at the departmental level. Patients and Methods: This single-center retrospective study was conducted at an acute care community hospital in Japan, which has 21 clinical departments and 250 inpatient beds, including four intensive care unit beds. We retrospectively analyzed trends in inpatient antimicrobial use from May 2019 to March 2023 using DASC to assess the effectiveness of a newly instituted antimicrobial stewardship program. Results: DASC/DOT in the Otolaryngology and respiratory medicine wards showed a significant decreasing trend, but a significant increase was observed in both the surgery and general practice wards. We observed no significant trends in the other wards. In the surgery and respiratory medicine wards, broad-spectrum antimicrobials such as carbapenems were frequently used. Conclusion: DASC highlighted differences in the trends of antimicrobial de-escalation at the ward level and identified targets for antimicrobial stewardship intervention.