The Minimum Important Difference for the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form in Women with Stress Urinary Incontinence

IntroductionMinimum important difference (MID) estimates the minimum degree of change in an instrument's score that correlates with a patient's subjective sense of improvement. We aimed to determine the MID for the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form (ICIQ-UI SF) using both anchor based and distribution based methods derived using data from the Trial of Midurethral Slings (TOMUS). Materials and MethodsInstruments for the anchor-based analyses included the urogenital distress inventory (UDI), incontinence impact questionnaire (IIQ), patient global impression of improvement (PGI-I), incontinence episodes (IE) on 7-day bladder diary, and satisfaction with surgical results. After confirming moderate correlation (r0.3) of ICIQ-UI SF and each anchor, MIDs were determined by calculating the difference between the mean instrument scores for individuals with the smallest amount of improvement and with no change. The distribution-based method of MID assessment was applied using effect sizes of 0.2 and 0.5 SD (small to medium effects). Triangulation was used to examine these multiple MID values in order to converge on a small range of values. ResultsAnchor-based MIDs range from -4.5 to -5.7 at 12 months and from -3.1 to 4.3 at 24 months. Distribution-based MID values were lower. Triangulation analysis supports a MID of -5 at 12 months and -4 at 24 months. ConclusionThe recommended MIDs for ICIQ-UI SF are -5 at 12 months and -4 at 24 months. In surgical patients, ICIQ-UI SF score changes that meet these thresholds can be considered clinically meaningful. Neurourol. Urodynam. 34:183-187, 2015. (c) 2013 Wiley Periodicals, Inc.