Determining the importance of change in the overactive bladder questionnaire

The overactive bladder questionnaire assesses symptom bother and health related quality of life in patients with overactive bladder. It has been shown to be reliable, valid and responsive. We established the minimally important difference of the overactive bladder questionnaire.

Post hoc analyses from 2 clinical trials were performed. Distribution based, eg effect size, and anchor based analyses using perception of treatment benefit and clinical variables were used.

The mean age of the 2 study populations was 58.8 and 58.7 years, respectively. Patients were predominantly female (51.8% and 75.1%) and white (83.9% and 87%, respectively). Half SD of the overactive bladder questionnaire symptom bother subscale was 9.1 to 9.3, and half SD of the overactive bladder questionnaire health related quality of life subscales (coping, concern, sleep and social interaction) was 9.8 to 13.2. Questionnaire subscales had moderate to large effect sizes with the largest effect sizes for symptom bother (-0.85 to -1.09). Anchor based analyses showed that significantly greater change scores were associated with greater patient perceived treatment benefit and satisfaction. The difference between change scores in patients perceiving no and little benefit was 7.4 to 16.5 for all questionnaire scales except social interaction with the majority greater than 10 points. Greater change scores were consistently associated with greater improvements in micturition diary variables.

Multiple methodologies provide strong justification for the recommendation of a 10-point minimally important difference for all overactive bladder questionnaire subscales. This minimally important difference may be conservative for some subscales, although a uniform minimally important difference is recommended to facilitate interpretation of the overactive bladder questionnaire.