Responsiveness and Minimal Clinically Important Change in Overactive Bladder Symptom Score

Abstract

To assess the responsiveness and minimal clinically important change (MCIC) in the Overactive Bladder Symptom Score (OABSS), a single score used to quantify overactive bladder symptoms. The data were derived from a clinical trial of propiverine in patients with overactive bladder. The analysis included participants who completed the OABSS, a bladder diary, and patient-reported outcome measures (urgency and incontinence impact) at baseline and 12 weeks. Responsiveness was assessed with effect sizes, correlations between the OABSS items and bladder diary variables, and comparisons between the score changes and symptom improvement. The MCIC was comprehensively estimated from the discriminating thresholds for minimal symptom improvement, and the receiver operating characteristics curve analyses were used to derive cutoff scores for symptom improvement. A total of 282 participants were included in the present analysis. The effect sizes for the OABSS ranged from -0.369 to -1.485, and correlations between the changes in the OABSS items and the corresponding bladder diary variables were moderate to large. A linear tendency was found between the changes in the OABSS and symptom improvement. The mean change for urgency and incontinence impact was -2.59 and -2.49 for "no change" and -3.67 and -3.78 for "minor improvement," respectively. The optimal cutoff score ranged from -4 to -3. Integrating the MCIC analyses, -3 was estimated as the minimal threshold for a meaningful change. With good responsiveness, the OABSS is a useful tool for assessing the treatment of OAB symptoms. Furthermore, the results of our study suggest that the MCIC of the OABSS is -3.