Validation of the Pelvic Floor Distress Inventory (PFDI-20) and Pelvic Floor Impact Questionnaire (PFIQ-7) in a Dutch population

Abstract

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. 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. 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. 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.