Responsiveness, Smallest Detectable Change, and Minimal Important Change of the Turkish Pelvic Floor Distress Inventory-20 Following Pelvic Floor Muscle Training

Background and Purpose: The Pelvic Floor Distress Inventory-20 (PFDI-20) is a widely recognized clinical tool designed to assess the severity of distress caused by pelvic floor symptoms. Within the context of conservative physiotherapy and pelvic floor rehabilitation, this study aimed to determine the responsiveness, smallest detectable change (SDC), and minimal important change (MIC) of the Turkish PFDI-20 in women with pelvic floor dysfunction (PFD). Methods: This multicenter, retrospective study consisted of 200 women (mean age, 46.92 ± 11.13 years) with PFD recruited across three clinical sites who had undergone a standardized 8-week conservative pelvic floor muscle training intervention. The PFDI-20, which includes three subscales (Pelvic Organ Prolapse Distress Inventory [POPDI-6], Colorectal-Anal Distress Inventory [CRADI-8], and Urinary Distress Inventory [UDI-6]), was administered at baseline and follow-up clinical assessments. The instrument's responsiveness was assessed using the Wilcoxon signed-rank test, standardized response means (SRMs), and effect sizes (ESs). The preliminary SDC estimates were calculated at the 95% confidence level. Receiver operating characteristic (ROC) analysis was used to determine preliminary MIC values, maximizing both sensitivity and specificity. Results: For PFDI-20 and UDI-6, the responsiveness was excellent (ES: 1.24, SRM: 1.41, for PFDI; ES: 1.47, SRM: 1.53, for UDI-6), moderate to good (ES: 0.78, SRM: 0.94), and moderate (ES: 0.55, SRM: 0.76) for POPDI-6 and CRADI-8, respectively. The preliminary SDC and MIC values were 55.60 and 20.83, 23.39 and 20.83, 17.71 and 9.37, 29.13 and 25.00, for PFDI-20, POPDI-6, CRADI-8, and UDI-6, respectively. The ROC analyses showed moderate to excellent discriminative ability, with an area under the curve of 0.85, 0.72, 0.72, and 0.85 for PFDI-20, POPDI-6, CRADI-8, and UDI-6, respectively. Discussion: These findings support the responsiveness of the Turkish PFDI-20 when applied in a conservative physiotherapy setting, providing preliminary estimates, specifically a SDC of 55.60 alongside a MIC of 20.83. However, derived from an active intervention cohort and imbalanced anchor groups, these values should be interpreted with caution as practical response thresholds within longitudinal clinical evaluations.