WISQOL (Wisconsin Stone Quality of Life questionnaire) is a disease specific, health related quality of life measure designed for patients who form kidney stones. The purpose of this study was to demonstrate the external and convergent validity of WISQOL and assess its psychometric properties.Materials and Methods:
At the WISQOL creation site (development sample) and at 8 geographically diverse centers in the United States and Canada (consortium sample) patients with a history of kidney stones were recruited. Item response option variability, correlation patterns and internal consistency were compared between samples. Convergent validity was assessed by patients who completed both WISQOL and SF-36v2® (36-Item Short Form Health Survey, version 2).Results:
Results were analyzed in 1,609 patients, including 275 in the development sample and 1,334 in the consortium sample. Response option variability patterns of all items were acceptable. Internal WISQOL consistency was acceptable. Intersample score comparisons revealed few differences. For both samples the domain-total WISQOL score correlations exceeded 0.86. Item level analyses demonstrated suitable variation, allowing for discriminatory scoring. At the time that they completed WISQOL, patients with stones and stone related symptoms scored lowest for health related quality of life. Patients with stones but no symptoms and those with no stones scored higher. The convergent validity substudy confirmed the ability of WISQOL to identify stone specific decrements in health related quality of life that were not identified on SF-36v2.Conclusions:
WISQOL is internally consistent and discriminates among patients with different stone statuses and symptoms. WISQOL is externally valid across the North American population. It may be used for multicenter health related quality of life studies in kidney stone disease.