Aims

The Michigan Incontinence Symptom Index (M-ISI) is a validated measure for urinary incontinence. This study evaluates the M-ISI as a screening tool for clinically relevant urinary incontinence in a population-based sample of women.

Methods

The Establishing the Prevalence of Incontinence (EPI) Study is a case-control, population-based study that enrolled women ages 35-64, with and without urinary incontinence. The M-ISI is a validated questionnaire with subdomains for stress and urgency urinary incontinence. Two hundred fourteen EPI subjects underwent a clinical evaluation and urodynamic testing to establish the presence and type of urinary incontinence, and also completed the M-ISI. The M-ISI scores were evaluated using receiver operating characteristic (ROC) curves to determine the optimal diagnostic threshold scores above which women were likely to have clinically relevant urinary incontinence.

Results

The optimal M-ISI diagnostic threshold scores were determined to be ≥ 3 for the stress urinary incontinence subdomain (area under the curve of 0.79), ≥ 5 for the urgency urinary incontinence subdomain (area under the curve of 0.88), and ≥ 7 for the Total M-ISI score (area under the curve of 0.89). The sensitivity and specificity of the M-ISI questionnaire for stress, urgency, and total urinary incontinence were 77% and 73%, 86% and 76%, and 84% and 75%, respectively.

Conclusions

The M-ISI may be used to screen for clinically relevant urinary incontinence with high sensitivity and specificity among women ages 35-64. A brief, self-administered tool such as the M-ISI can help health care providers identify and manage women with urinary incontinence.

Aims

To develop a clinically relevant, easy to use, and validated instrument for assessing severity and bother related to urinary incontinence.

Methods

Survey items were piloted and refined following psychometric principles in five separate patient cohorts. Patient and expert endorsement of items, factor analyses, Spearman rank correlations and response distributions were employed for item selection. Formal reliability and validity evaluation were conducted for the final questionnaire items.

Results

Expert physicians and patient focus groups confirmed face and content validity for the measure. A 10-item measure called the Michigan Incontinence Symptom Index (M-ISI) was developed with two domains: a Total M-ISI Domain consisting of subdomains for stress urinary incontinence, urgency urinary incontinence, and pad use, and a Bother Domain. High construct validity was demonstrated with a Cronbach's alpha for the Total M-ISI Domain (items 1-8) of 0.90 and for the Bother Domain (items 9-10) of 0.82. Cronbach's alpha for the subdomains were all > 0.85. Construct validity, convergent and divergent validity, internal discriminant validity, and predictive validity were all robust. The minimally important difference for the measure was determined to be 4 points (out of 32) for the Total M-ISI Severity Domain, and 1-2 points (out of 8-12) for the individual subdomains.

Conclusions

The M-ISI is a parsimonious measure that has established reliability and validity on several levels and complements current clinical evaluative methods for patients with urinary incontinence.