Emergency department urine culture stewardship and downstream outcomes: a covariate-adjusted biweekly interrupted time series analysis.

Background: Emergency department (ED) urine culture stewardship may reduce low-value testing, but downstream effects on antibiotic use and postdischarge utilization remain uncertain. Methods: We evaluated an intervention in which an infectious diseases physician and microbiologist reviewed pyuric urinalysis-with-reflex encounters, assessed culture indications, and contacted clinicians to recommend cancellation when absent. Adult ED encounters from February-July 2025 to September 2025-February 2026 were included; August was washout. Outcomes were urinalysis with reflex within 24 hours, urine culture within 24 hours, antibiotic days of therapy (DOT) per 100 patient-days, length of stay (LOS), and 30-day ED revisit among ED discharges. We fit biweekly interrupted time series models. Results: Among 17,621 encounters, the intervention was associated with lower postintervention slopes for urinalysis with reflex within 24 hours (-0.5 percentage points per biweekly period; 95% CI, -0.9 to -0.1) and urine culture within 24 hours (-0.2 percentage points; 95% CI, -0.4 to -0.0). DOT showed no sustained change (postintervention slope change, 0.00; 95% CI, -0.23 to 0.24). LOS showed a lower postintervention slope (-0.05 d; 95% CI, -0.08 to -0.02). Thirty-day ED revisit showed a higher postintervention slope (0.8 percentage points; 95% CI, 0.3 to 1.3). Conclusions: The intervention reduced urinary testing but did not reduce antibiotic DOT and was associated with increased 30-day ED revisit. Diagnostic stewardship in the ED may need to be paired with antimicrobial stewardship and prospective safety monitoring.