Reliability and validity of the incontinence quality of life questionnaire in patients with neurogenic urinary incontinence

Objective: To assess the reliability, validity, responsiveness and minimally important difference (MID) of the Incontinence Quality of Life (I-QOL) questionnaire in patients with urinary incontinence due to neurogenic detrusor overactivity. Design: Randomized, double-blind, multicenter, placebocontrolled study. Setting: Eight centers across Belgium, France, and Switzerland. Participants: Patients with urinary incontinence due to neurogenic detrusor overactivity inadequately managed on oral anticholinergics. Fifty-nine patients (spinal cord injury, n=53; multiple sclerosis, n=6) were enrolled. Intervention: Single dose of botulinum toxin type A (Botox) (200 or 300U) or placebo. Main Outcome Measures: I-QOL questionnaire completed at screening and over a 24-week post-treatment period. Results: The Cronbach a ranged from.79 to.93, indicating that I-QOL is a reliable measure of QOL in neurogenic urinary incontinence patients. No item had more than 5.1% missing or out of range values. With the exception of 2 items, questions showed acceptable item-scale correlation and scaling success results varied by domain. Post-treatment correlations indicated acceptable construct validity. The I-QOL was responsive to improvements in symptoms. MID values ranged from 4 to 11 points. Conclusions: Results suggest that I-QOL is a reliable, valid, and responsive measure of incontinence-related QOL in neurogenic patients.