The guidance ratio: a measure of post-diagnostic antibiotic decision-making.

BACKGROUND: Scalable measures that capture post-diagnostic antibiotic decisions are lacking. We developed and validated the guidance ratio (GR), a registry-based measure of post-diagnostic antibiotic decision-making. METHODS: We conducted a retrospective multi-centre validation study of the GR and discontinuation ratio (DR), two registry-based indicators of post-diagnostic antibiotic decision-making in paediatric febrile urinary tract infection. Prescribing outcomes were classified using rule-based algorithms and compared with manually classified outcomes from medical record review. Indicator performance was evaluated against medical record data used as the reference standard. RESULTS: Among 909 episodes, the GR identified guided treatment with a sensitivity of 0.78 and specificity of 1.00. Although registry-based estimates underestimated absolute values, they closely tracked temporal prescribing patterns. Calibration substantially improved agreement with manually classified outcomes. CONCLUSIONS: The GR captured clinically meaningful prescribing patterns and may support scalable monitoring of post-diagnostic antibiotic decision-making in stewardship programmes.