Objectives: To report on the further development of the Incontinence Quality of Life Instrument (I-QOL), a self-report quality of life measure specific to urinary incontinence (UI), including its measurement model, responsiveness, and effect size.
Methods: Incontinent female patients (141 with stress, 147 with mixed UI) completed the I-QOL and comparative measures at screening, pretreatment, and four subsequent follow-up visits during participation in a multicenter, double-blind, placebo-controlled, randomized trial assessing the efficacy of duloxetine. Psychometric testing followed standardized procedures.
Results: Factor analysis confirmed an overall score and three subscale scores (avoidance and limiting behaviors, psychosocial impacts, and social embarrassment). All scores were internally consistent (alpha = 0.87 to 0.93) and reproducible (ICC = 0.87 to 0.91). The pattern of previously reported correlations with the Short-Form 36-item Health Survey and Psychological Well-Being Schedule were confirmed. Responsiveness statistics using changes in the independent measures of stress test pad weight, number of incontinent episodes, and patient global impression of improvement ranged from 0.4 to 0.8. Minimally important changes ranged from 2% to 5% in association with these measures and effect sizes.
Conclusions: In a clinical trial, the I-QOL proved to be valid, reproducible, and responsive to treatment for UI in women.