The minimum important differences for the urinary scales of the Pelvic Floor Distress Inventory and Pelvic Floor Impact Questionnaire

OBJECTIVE: We sought to estimate the minimum important difference (MID) for the Urinary Distress Inventory (UDI), UDI-stress subscale of the Pelvic Floor Distress Inventory, and Urinary Impact Questionnaire (UIQ) of the Pelvic Floor Impact Questionnaire. STUDY DESIGN: We calculated MID using anchor- and distribution-based approaches from a randomized trial for nonsurgical stress incontinence treatment. Anchors included a global impression of change, incontinence episodes from a urinary diary, and the Incontinence Severity Index. Effect size and standard error of measurement were the distribution methods used. RESULTS: Anchor-based MIDs ranged from -22.4 to -6.4 points for the UDI, -16.5 to -4.6 points for the UDI-stress, and -17.0 to -6.5 points for the UIQ. These data were supported by 2 distribution-based estimates. CONCLUSION: Reasonable estimates of MID are 11, 8, and 16 points for the UDI, UDI-stress subscale, and UIQ, respectively. Statistically significant improvements that meet these thresholds should be considered clinically important.