Researchers for the Urinary Incontinence Treatment Network found that the minimum important difference for the Urogenital Distress Inventory was –35 to –45 points in patients with urge urinary incontinence.
St. Petersburg, FL-How much improvement does it take to make a real clinical difference in urge incontinence patients? When using questionnaires to measure outcomes in clinical research, the change in score that is clinically important is often unknown.
The Urogenital Distress Inventory (UDI) is one of a few validated instruments used to measure patients' degree of bother with urinary symptoms. Researchers for the Urinary Incontinence Treatment Network (UITN) found that the minimum important difference for the UDI was –35 to –45 points in patients with urge urinary incontinence. This analysis was based on the BE-DRI (Behavior Enhances Drug Reduction of Incontinence) study, in which some 300 women with pure urge or urge-predominant incontinence completed the UDI, the Incontinence Impact Questionnaire (IIQ), and the Overactive Bladder Questionnaire (OAB-q) at baseline and several times during follow-up. The patients also completed more global questionnaires and filled out voiding diaries.
Keisha Dyer, MD, MPH, who presented the analysis at the Society for Urodynamics and Female Urology winter meeting, explained the investigators' rationale.
Using BE-DRI data, the team compared the changes assessed with the urologic questionnaires with subjective and objective "anchors": the Global Perception of Improvement and Patient Satisfaction Questionnaires and the number of incontinence episodes noted in voiding diaries. In addition, the team also used a distribution-based method with various effects sizes to determine minimum important difference in scores on these questionnaires. Only the UDI met the team's criteria for both types of analysis.
No change in MID over time
The minimum important difference (MID) on the UDI for these patients turned out to be –35 to –43 points with the subjective anchors and –36 to –45 points for the objective anchors. Furthermore, the MID did not change with time. Based on a post-hoc threshold analysis, a UDI score of 100 or less at 10 weeks after treatment had a sensitivity of 90% and a specificity of 71% to detect satisfaction. The team concluded that the MID for the UDI was –35 to –45 points in patients with urge urinary incontinence. That difference is much higher than the MID of 11 points on the UDI that Barber et al determined for patients with stress urinary incontinence (Am J Obstet Gynecol 2009; 200:580.e1-7).
Several studies suggest that patients with urge have more bother than stress incontinence patients, and when patients have mixed incontinence, the urge component is often more bothersome than the stress component, said Dr. Dyer.
"Our study echoes these findings and suggests that patients with urge incontinence may require a higher degree of improvement in their symptoms in order to have a sense of satisfaction with treatment. In the future, these MIDs will allow us to design patient-centered outcomes studies using instruments like the UDI as primary outcome measures," Dr. Dyer concluded.
Dr. Dyer and her UITN team received funding and support from Pfizer, as well as grants from the National Institute of Diabetes and Digestive and Kidney Diseases.