Reliability and validity of the Japanese version of the pelvic floor distress inventory-short form 20

Introduction and hypothesis: The aim of this study was to translate the Pelvic Floor Distress Inventory-Short Form 20 (PFDI-20) into Japanese and test its reliability and validity among Japanese women. Methods: Fifty-nine women with and without pelvic floor disorders (age 55.8 ± 16.8 years, mean ± SD) completed the Japanese PFDI-20 (J-PFDI-20) questionnaire at baseline and 2 weeks later. Intraclass correlation coefficients (ICC) and the Bland and Altman method for test-retest reliability and Cronbach's alpha for internal consistency of the J-PFDI-20 were used. Scores of total and subscales were compared between women with and without pelvic floor disorders for known-groups validity. Spearman's correlation coefficients between the J-PFDI-20 and the severity of pelvic floor disorders and Urinary Incontinence Quality of Life Scale (I-QOL) were used for construct validity. Results: The PFDI-20 was successfully translated from English into Japanese with face validity through rigorous cross-cultural validation. Test-retest reliability of the J-PFDI-20 and three subscales was good to excellent (ICC = 0.77-0.90). The Bland and Altman analysis showed that differences between the first and second scores of total J-PFDI-20 and its subscales were not significantly different from 0 and largely fell within the range of 0 ± 1.96 SD. Cronbach's alpha values were 0.52-0.83. Analysis of known-groups validity showed differences in scores of the J-PFDI-20 between women with and without pelvic floor disorders. Acceptable construct validity was found in J-PFDI-20 total and subscale scores with positive correlations to severity of pelvic floor disorders (ρ > 0.35) and negative correlations to I-QOL (ρ < -0.39). Conclusions: The results suggest that the J-PFDI-20 is a reliable and valid condition-specific quality of life instrument for women with pelvic floor disorders.