Korean Standardized Antimicrobial Administration Ratio in Long-Term Care Hospitals: A Benchmark Tool

Background Antimicrobial stewardship in long-term care hospitals (LTCHs) is increasingly important ; however, standardized benchmarking tools for antimicrobial use in these settings are lacking. The Korean Standardized Antimicrobial Administration Ratio for long-term care hospitals (K-SAAR–LTCHs) was developed to benchmark antimicrobial use in these facilities. Methods We used 2021 National Health Insurance claims data from 1,432 LTCHs (232,826 inpatients) in Korea. Data were split into training (80%) and test (20%) sets for model validation. Main outcome measure was measured in defined daily doses per 1,000 patient-days (DPD). Predicted antimicrobial use was estimated using a negative binomial regression model, selected by the Akaike Information Criterion (AIC) for best model fit. Predictive performance was evaluated using mean absolute percentage error (MAPE) and coefficient of determination (R²). The standardized antimicrobial administration ratio (SAAR) was calculated as observed-to-predicted antimicrobial use for each LTCH. Results Antimicrobial use under fee-for-service payment was substantially higher than under fixed-rate payment (1,199.3 vs 82.6 DPD). Higher antibiotic use was associated with male sex, severe illness, and indwelling catheter use, whereas greater pharmacist staffing was linked to lower use. Mean SAAR values for pneumonia and septicemia were approximately 1.0, indicating overall antimicrobial use near predicted levels. However, 19.6% of hospitals exceeded expected use for pneumonia and 5.2% for septicemia. Model performance was robust (MAPE 1.2–2.6; R² up to 0.93). Conclusions The K-SAAR–LTCHs model enables risk-adjusted benchmarking of antimicrobial use in LTCHs. This model identifies institutional variability and supports data-driven antimicrobial stewardship, offering an evidence-based foundation for national surveillance and quality improvement in Korea.