Administrative data-based assessment of oral antibiotic prescribing for acute upper respiratory tract infections using the WHO AWaRe classification: a single-center retrospective study at a tertiary care outpatient setting in Japan (2020-2024).

Outpatient antibiotic use for acute upper respiratory tract infections contributes to antimicrobial resistance, yet data from Japanese tertiary outpatient settings are limited. We retrospectively reviewed outpatient encounters at National Hospital Organization Osaka National Hospital (Osaka, Japan) from April 2020 to March 2024 with ICD-10 diagnoses J00, J01, J02, or J06. Oral antibiotic prescriptions were mapped to the 2022 World Health Organization Access/Watch/Reserve classification and assessed using a conservative, guideline-derived operational framework across indication, agent, and intended duration; multivariable logistic regression evaluated factors associated with algorithm-defined guideline nonconcordance. Among 2,431 encounters, antibiotics were prescribed in 19.5% (475/2,431). Watch-group agents accounted for 64.0% (304/475). Under the operational criteria, 92.2% (438/475) of prescriptions were algorithm-defined guideline-nonconcordant, most often because antibiotics were not indicated for the recorded diagnosis. Nonconcordant prescribing was strongly associated with age ≤12 years (adjusted odds ratio [aOR] 7.56) and acute pharyngitis (aOR 2.56 vs acute rhinosinusitis). Because assessment relied on ICD-10 and prescription data, these estimates should be interpreted as algorithm-defined guideline nonconcordance rather than definitive clinical inappropriateness. Findings highlight priorities for outpatient antimicrobial stewardship and support prospective validation with chart-level clinical data and microbiological testing.