Evaluating the 8-item overactive bladder questionnaire (OAB-v8) using item response theory

The OAB-v8 is a patient-reported outcome questionnaire used to screen for overactive bladder and measure symptom bother. This study uses modern validation methods to assess the item and test characteristics of the OAB-v8, and determine whether it should be scored differently for men and women.

A secondary analysis of data from patients with lower urinary tract symptoms prospectively recruited from a urology clinic in Calgary, Canada. Item-response theory (IRT) was used to evaluate the dimensionality, reliability, and validity of the OAB-v8, and differential functioning analysis (DIF) was used to determine whether the OAB-v8 should be scored differently for men and women.

A total of 1128 patients were included for analysis, of which 28% were female. Mean OAB-v8 scores indicated meaningful levels of symptom bother, and women scored 2 points higher, on average, than men (P = 0.005). Reliability was high (Cronbach's alpha = 0.901) for a wide range of patients (between -2 and 2.5 standard deviations of the mean). Samejima's graded response model best fit the data, and the scale demonstrated essential unidimensionality. Items #5 and #6 were excessively correlated. There was no evidence of differential functioning.

OAB-v8 demonstrated high reliability and would be appropriate for a wide range of patients. Items #5 and #6 may need to be re-worded. The OAB-v8 should not be scored differently for men and women, although women do appear to experience higher average levels of symptom bother from OAB than men.

Neurourology and urodynamics. 2017 Oct 04 [Epub ahead of print]

Alexander C Peterson, Anika Sehgal, R Trafford Crump, Richard Baverstock, Jason M Sutherland, Kevin Carlson

Centre for Health Services and Policy Research, University of British Columbia, Vancouver, British Columbia, Canada., Vesia [Alberta Bladder Centre], Calgary, Alberta, Canada., Department of Surgery, University of Calgary, Calgary, Alberta, Canada.