Development and Validation of a Nomogram for Predicting Urinary Tract Infection After Urodynamic Study

INTRODUCTION: The use of antibiotic prophylaxis before urodynamic studies has been debated for a long time, with no clear consensus among international guidelines. Based on identified predictors of urinary tract infection after urodynamic studies, this study aims to develop and internally validate a nomogram to predict post-urodynamic study urinary tract infection and assess its clinical net benefit to support selective antibiotic prophylaxis. METHODS: Multivariable logistic regression identified final predictors; coefficients were converted into a user-friendly nomogram. Performance was evaluated using the area under the receiver operating characteristic curve (ROC-AUC), Brier score, calibration (bootstrap-corrected), and precision-recall AUC (average precision). Decision curve analysis was used to evaluate the clinical net-benefit of the nomogram. RESULTS: The nomogram includes five routinely available variables: hydronephrosis, neurological lower urinary tract dysfunction, post-void residual volume ≥ 200 mL, age ≥ 70, and the use of an indwelling catheter or performing clean intermittent catheterization. Discrimination was fair (ROC AUC 0.7086). Overall accuracy was good (Brier 0.0180). Calibration showed good agreement after bootstrap correction. Average precision was 0.0508, exceeding the base prevalence. Decision curve analysis demonstrated a positive net benefit relative to both the treat-all and treat-none strategies at low clinical thresholds (