Adaptation and validation of the Michigan Incontinence Severity Index in a Turkish population

OBJECTIVE To translate and validate the Michigan Incontinence Severity Index (M-ISI) for its use in Turkish-speaking women with urinary incontinence. METHODS The translation and cross-cultural adaptation were based on international guidelines. Content validity by content validity ratio/content validity index, internal consistency by Cronbach's alpha, test-retest reliability by Pearson's correlation, and construct validity by using Spearman rank correlations to show the relationship between individual items and the relevant domains and subdomains were analyzed in 100 female participants with a chief complaint of urinary incontinence. Correlations between the relevant scores of M-ISI and The International Consultation on Incontinence Questionnaire - Short Form scores were analyzed to indicate convergent validity. The Varimax rotation method was used to conduct exploratory factor analysis in order to investigate the factor structures/distribution of M-ISI items. RESULTS Content validity index and content validity ratio values increased to 0.97 and 1.00, respectively, showing sufficient content validity of the Turkish version of the M-ISI. The analysis formed three factors which was slightly different from original developers. In our proposed three-factor construct, all of the ten items demonstrated high correlations with their subdomains and lower correlations with the other domains, indicating good construct validity. Correlations between stress urinary incontinence and urge urinary incontinence (UUI) scores and The International Consultation on Incontinence Questionnaire - Short Form scores were found high, which indicated convergent validity (r: 0.953, P<0.001). Good internal consistency of the scores for each subdomain was observed (stress urinary incontinence, 0.787; UUI, 0.862; pad usage and bother, 0.832). Test-retest reliability was shown for each subdomain (stress urinary incontinence, 0.973; UUI, 0.973; pad usage and bother, 0.979). CONCLUSION The translated and cross-culturally adapted M-ISI showed good validity, reproducibility, and reliability that allow its use in Turkish-speaking populations with urinary incontinence. Its comprehensive structure means that it has become a practical instrument that is available for utilization in the primary health care setting, clinical research, and epidemiological trials in Turkey.