The Recurrent Urinary Tract Infection Symptom Scale: Responsiveness to Antibiotic Treatment and the Minimal Clinically Important Difference.

OBJECTIVE

To evaluate the responsiveness of the Recurrent Urinary Tract Infection Symptom Scale (RUTISS) to antibiotic treatment and determine the minimal clinically important difference (MCID).

METHODS

Female adults with recurrent UTI (N = 108, mean age = 53.6 years) completed a repeated-measures, longitudinal, 40-day naturalistic follow-up study. For participants initiating and completing antibiotic treatment within this period, RUTISS scores were evaluated at baseline (2 days pre-treatment), day 1 of treatment, day 3, and at follow-up (7 days post-treatment). Responsiveness was assessed using effect sizes pre- and post-treatment (rank-biserial correlation), Spearman's rank correlations with anchor measures (Patient Global Impression of Change, PGIC, and UTI Symptom Assessment, UTISA), and receiver operating characteristic analysis. The MCID was triangulated via anchor- and distribution-based methods.

RESULTS

The RUTISS total score demonstrated excellent responsiveness between all timepoints and was strongest between baseline and day 3 (rank-biserial r = 0.52), with strong correlations with the PGIC (Spearman's ρ = 0.73) and UTISA (Spearman's ρ = 0.63). Receiver operating characteristic analysis indicated excellent discrimination for detecting even minimal improvement (AUC = 0.82). The recommended MCID was 6.5 points, exceeding the standard error of measurement. All subscales demonstrated good to excellent responsiveness.

CONCLUSION

The RUTISS demonstrates excellent responsiveness to antibiotic treatment providing a validated MCID, enabling precise interpretation of treatment effects. As the first fully validated PROM for recurrent UTI, the RUTISS addresses a critical unmet need to assess patient symptom reporting. By providing a responsive and interpretable patient-centered endpoint, the RUTISS enables adequately powered clinical trials and evidence-based symptom monitoring, directly supporting improved patient care and intervention development.