Reliability and validity of King's Health Questionnaire in patients with symptoms of overactive bladder with urge incontinence in Japan

Abstract

The purpose of this study is to evaluate the psychometric properties of the Japanese version of the King's Health Questionnaire (KHQ) in patients with symptoms of overactive bladder (OAB) with urge incontinence. Data from a 12-week, randomized, double-blind, placebo-controlled clinical trial comparing tolterodine with oxybutynin in patients with symptoms of OAB in Japan were analyzed. Cronbach's alpha coefficient was calculated as a reliability index. Inter-domain correlation was calculated for convergent and discriminant validity assessment. A factor analysis was conducted to explore the underlying factor structure of the KHQ. Sensitivity to clinical change was also evaluated. The psychometric properties and clinical validity of the KHQ Japanese version were confirmed in this study population, and were similar between males and females. The KHQ's good reliability was evidenced by Cronbach's alpha coefficients of >0.60, indicating reasonable consistency except for the personal relationship domain in males (0.47) and severity (coping) measure domain in females (0.59). Discriminant, convergent, and construct validity of the KHQ were also good, with the factor analysis identifying those factors which the KHQ was intended to measure. Finally, KHQ domains were generally responsive to clinical efficacy variables; the KHQ also showed statistically significant sensitivity to change in patients' perception of bladder condition in all domains, except General Health Perception. Our analyses confirm psychometric properties and clinical validity of the KHQ Japanese version, which appears to offer a valid and reliable HRQoL instrument for use in clinical trials of antimuscarinics in Japan.