Elsevier

Urology

Volume 67, Issue 6, June 2006, Pages 1304-1308
Urology

Basic science
Minimal clinically important differences in Incontinence Quality-of-Life scores in stress urinary incontinence

https://doi.org/10.1016/j.urology.2005.12.006Get rights and content

Abstract

Objectives

To determine the clinically relevant reference points for the Incontinence Quality of Life (I-QOL) questionnaire scores in women with stress urinary incontinence and compare them with the treatment effects observed with duloxetine and placebo.

Methods

Using data from 1133 women with predominant stress urinary incontinence in two randomized, placebo-controlled duloxetine studies, the within-treatment and between-treatment minimal clinically important differences (MCIDs) were obtained by anchoring the I-QOL scores to the validated Patient Global Impression of Improvement scale (PGI-I). The within-treatment MCID (mean I-QOL for women rating their condition “a little better” with treatment) and between-treatment MCID (difference in scores between the group ratings of “no change” and “a little better”) were derived. The treatment effects were compared with these MCIDs. Real-time urinary diaries were completed, along with the I-QOL and PGI-I.

Results

The within-treatment and between-treatment MCID for the I-QOL total score was 6.3 and 2.5, respectively. The total and subscale scores had almost identical MCIDs. Duloxetine 80 mg significantly improved the I-QOL total and subscale scores. Treatment differences in the I-QOL scores exceeded the between-treatment MCID and the duloxetine I-QOL treatment effect exceeded the within-treatment MCID. The number of patients needed to treat to gain an additional I-QOL responder was 6.8.

Conclusions

Improvements in I-QOL scores should be greater than the within-treatment MCID, and differences between two treatments should be greater than the between-treatment MCIDs, for statistically significant differences to be considered clinically meaningful. We propose 2.5 points as a reasonable guide for the I-QOL between-treatment MCID and 6.3 points for the within-treatment MCID.

Section snippets

Material and methods

Women with SUI were enrolled in two double-blind, controlled, randomized studies of duloxetine versus placebo.8, 9 One study randomized 553 women and the other 580 women at U.S. study sites. Predominant SUI was diagnosed using a clinical algorithm demonstrated to be 90.2% predictive of urodynamic stress incontinence.13

We used the Patient Global Impression of Improvement (PGI-I) rating as the anchor for this MCID analysis. It is a validated, single-item global rating of change scale that asks

Results

A total of 1133 women were randomized to duloxetine 20 mg/day (n = 138), 40 mg/day (n = 137), or 80 mg/day (n = 433) or placebo (n = 425). The mean age was 51.1 years; 50.9% had a body mass index of 28 kg/m2 or more; and 91% were white. The mean baseline IEF was 19.1/wk (SD 15.5), and the mean I-QOL score was 62.4 (SD 18.7).

Table I presents the I-QOL outcome data by PGI-I response category and demonstrates that the total and subscale scores had virtually identical between-treatment MCIDs,

Comment

This analysis has demonstrated that a reasonable guide for a clinically relevant increase in the I-QOL total score with treatment for women with SUI is ∼6.3 points (within-treatment MCID). The clinically relevant separation in improvements between two treatments is ∼2.5 points (between-treatment MCID). These thresholds are similar for the subscale scores, and the within-treatment MCID is similar to that previously reported in a study of 288 women with SUI and mixed urinary incontinence.7 Our

Conclusions

A score of 2.5 points can be considered a reasonable guide for the between-treatment and 6.3 points for the within-treatment MCID for the I-QOL total score. Statistically significant improvements in I-QOL scores should generally exceed both thresholds to be considered clinically important.

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  • OnabotulinumtoxinA improves health-related quality of life in patients with urinary incontinence due to idiopathic overactive bladder: A 36-week, double-blind, placebo-controlled, randomized, dose-ranging trial

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    This study shows the positive impact of onabotulinumtoxinA doses ≥100 U for patients with idiopathic OAB refractory to standard medical therapy. The improvements in HRQOL scores observed with onabotulinumtoxinA in this study exceeded previously documented minimally or clinically important differences for the I-QOL (between-treatment MID of 2.5 points) [18] and the KHQ (change from baseline of ≥5 points) [19]. It is noteworthy that patients in this study reported both a disease-specific quality of life and a general HRQOL at baseline.

  • Considering benefits and harms of duloxetine for treatment of stress urinary incontinence: A meta-analysis of clinical study reports

    2017, CMAJ
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    Duloxetine was better than placebo in terms of mean change in this score (mean difference 3.24, 95% CI 2.00 to 4.48, I2 = 5%; Figure 2). However, given that the published minimum clinically important difference for the Incontinence Quality of Life total score is 2.5,35 this difference may not be clinically important. Furthermore, the effect size for this outcome was small (standardized mean difference 0.24, 95% CI 0.15 to 0.33, I2 = 0%; Appendix 1).

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This study was sponsored by Eli Lilly and Company and Boehringer Ingelheim.

1

I. Yalcin, K. Summers, K. Kinchen, and R.C. Bump are employees of, and hold stock in, Eli Lilly. D.L. Patrick is a paid consultant to Eli Lilly.

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