Validation of the pelvic floor distress inventory (PFDI-20) and pelvic floor impact questionnaire (PFIQ-7) in a Dutch population

Introduction and hypothesis: The objective of this study was to validate the Pelvic Floor Distress Inventory (PFDI-20) and Pelvic Floor Impact Questionnaire (PFIQ-7) in Dutch women. Methods: Patients with pelvic floor dysfunction completed the Dutch questionnaires at (1) inclusion to evaluate internal consistency, (2) 1 week later to assess test-retest reliability, and (3) 6 months later to assess responsiveness and interpretability of change. To assess validity, floor and ceiling effects and construct validity were tested. A population-based sample (reference group) completed the questionnaires once. Results: Data of 111 patients and 283 reference group participants were analyzed. Internal consistency of baseline scores in patient and reference groups was moderate (Cronbach's alpha 0.52-0.60) to adequate in the PFDI-20 (Cronbach's alpha 0.71-0.84) and adequate in the PFIQ-7 (Cronbach's alpha 0.88-0.94). Both measures presented adequate test-retest reliability (intraclass correlation coefficient 0.79-0.91) and adequate responsiveness (area under the receiver-operating characteristic curve both 0.77). Interpretability was adequate for PFDI-20 and acceptable for PFIQ-7 with a clinically relevant minimally important change of -23 and -29 points, respectively. At baseline, the scales of the PFIQ-7 showed floor effects (44-55 %) in patients, though the PFIQ-7 summary score did not. No ceiling effects were observed. Construct validity was adequate with all predefined hypotheses confirmed regarding subgroup discrimination using pooled patient and reference group baseline data. Conclusions: For assessing distress and health-related quality of life of pelvic floor dysfunction, the Dutch PFDI-20 and PFIQ-7 are reliable and valid in the general Dutch population, and also responsive and interpretable among tertiary care-seeking women.

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