Multinational study of reliability and validity of the King's Health Questionnaire in patients with overactive bladder

Objective: Overactive bladder (OAB) has substantial impact on health-related quality of life (HRQoL). The purpose of this research was to evaluate the psychometric properties of the King's Health Questionnaire (KHQ). Methods: The KHQ (n = 1284) was administered at baseline and 12 weeks post-treatment in a multinational, double-blind, randomized clinical trial of tolterodine for treatment of OAB. Country-specific psychometric analyses of HRQoL instruments were performed. Countries demonstrating marginal psychometric properties on the KHQ were pooled with same-language countries, re-evaluated, and aggregate analysis performed on the pooled data. Results: Internal consistency of the KHQ was high, item characteristics were good, most assumptions of summed scales were met, and it is externally valid and consistent. Few problems with the KHQ were noted although the performance of the personal relationships domain was complicated by the 'not applicable' response category. Conclusions: Psychometric testing supports the reliability and validity of the KHQ as an OAB-specific measure of HRQoL.