Minimal clinically important change in urinary incontinence detected by a quality of life assessment tool in overactive bladder syndrome with urge incontinence

Aims: The objective of this research was to detect a minimal clinically important change (MCIC) in frequency of incontinence episodes in Japanese patients with overactive bladder syndrome (OAB) based on the change in domain scores of health-related quality of life (HRQoL). Methods: The patients (n = 659) enrolled for the 8 weeks, randomized, double-blind, placebo-controlled study of an oxybutynin transdermal patch were used for the analysis. The endpoints of the study were the change in frequency of incontinence episodes and the domain scores of King's health questionnaire (KHQ) from baseline to the end of treatment. To search a threshold of the change of incontinence frequency that apparently improves patient's quality of life (QOL), we calculated mean changes of selected five KHQ domain scores for nine patient groups divided by the amount of change of incontinence frequency. A minimum value of the change of incontinence frequency in the groups with apparent improvement in the QOL scores was defined as an MCIC of incontinence frequency. Results: The apparent improvement of KHQ domain scores was seen in the patient groups whose incontinence episodes decreased more than three times per week (/w) after treatment. This result was common in almost all domain scores, but more relevant for the domains related to patients' life limitations. Conclusion: Japanese OAB patients can feel their QOL improved if their incontinence episodes decrease more than 3 times/w. This suggests that the reduction of '3 times/w' is an MCIC of incontinence frequency for Japanese OAB patients.