Defining the Minimal Important Difference in International Prostate Symptom Score for Men with Lower Urinary Tract Symptoms Using a Patient-centered Anchor Measure.

Background and objective: Few studies have investigated the minimal important difference (MID) for the International Prostate Symptom Score (IPSS), which is essential for interpreting clinical outcomes after treatment for lower urinary tract symptoms (LUTS). The aim of our study was to determine the IPSS MID using data from a randomized controlled trial (RCT) evaluating an app-based intervention (Kranus Lutera) for LUTS in men. Methods: Patients with LUTS diagnosed with benign prostatic hyperplasia, overactive bladder, or both by office-based urologists across Germany were included. After following the Kranus Lutera app for LUT therapy for 12 wk, participants completed the IPSS and the Patient Global Impression of Change (PGIC) questionnaire. The MID, defined as the mean change from baseline in IPSS among 82 men who reported "minimally improved" on the PGIC, was calculated in a secondary exploratory analysis. Key findings and limitations: The MID calculated for the IPSS was 5.26 points (95% confidence interval [CI] 4.38-6.13). Stratified analysis revealed a higher MID in the subgroup with severe baseline symptoms (8.23; 95% CI 6.58-9.88) than for the subgroup with moderate symptoms (4.00; 95% CI 3.14-4.86). As the data were drawn from a single RCT, the generalizability may be limited, particularly for results for subgroups with small sample sizes. Conclusions and clinical implications: These findings provide a valuable reference for clinicians interpreting treatment outcomes and offer important insights for future trial design. Further research in larger and more diverse populations is essential to improve generalizability and external validation. Patient summary: We looked at results for the International Prostate Symptom Score (IPSS), a questionnaire used to assess lower urinary tract symptoms (LUTS) in men, to determine what patients feel is a meaningful improvement in symptoms. We used data from a clinical trial that tested an app to help men in improving their LUTS. Men felt that the minimum level of improvement for a benefit was change of 5.26 points in IPSS. Men with more severe symptoms at the start of treatment required greater improvements, while men with moderate symptoms needed smaller changes. These findings may help doctors in understanding the amount of improvement in symptoms that patients feel is significant, and could guide future LUTS treatments and trials.