Italian Validation of the Pelvic Floor Distress Inventory (PFDI-20) Questionnaire

The validation process of a linguistic translation must maintain conceptual and technical equivalence between the source and the target language. The questionnaire was translated into Italian by the following procedural steps. A preliminary translation from English into Italian was carried out in parallel by two native Italian-speaking translators, with English as their first foreign language. Then, a consensus meeting among translators and the research group was held to compare the two Italian versions and yielded a first consensus Italian version of the questionnaire. After that, a native English-speaking translator with Italian as his first foreign language back-translated the Italian consensus version. A second consensus meeting was held between the English mother-tongue translator and clinical investigators, during which the back-translated and the original questionnaires were compared and differences discussed. The process led to a revised version of the first consensus questionnaire. The comprehension of the obtained Italian consensus version was therefore tested in a real-life population to assess questionnaire comprehension. The questionnaire was submitted to women during a gynecological medical interview and they were asked to evaluate their perceived degree of difficulty in understanding each question item. After that, the final Italian version of the questionnaire was obtained.

The endpoint is the evaluation of the validity, internal consistency, and test-retest reliability.

Study participants will be patients referred to the urogynecological outpatient for pelvic floor disorders (genital prolapse and/or urinary incontinence). Cases and controls were defined, as done previously, with respect to bowel, bladder or prolapse symptoms using the question: "How much do your symptoms bother you?" and the following choice of answers: "Not applicable - I do not have symptoms", "not at all", "a little", "quite a lot" and "very much". Controls were identified as women answering "Not applicable - I do not have symptoms" or "not at all", otherwise patients were defined as cases.Patients will be asked to complete the self-reported questionnaire to evaluate the presence and the severity of pelvic floor symptoms. For the test-retest evaluation, cases will receive the questionnaire two weeks later by email. Questionnaire distribution and all interviews will be undertaken by the authors. Cases will report the identification code on the questionnaire in order to associate the first questionnaire with the retest one. Patients will return the retest questionnaire as soon as possible (by email or in outpatient).

Total scores for women with and without significant symptoms will be compared and tested for statistical differences in order to assess validity. Given the heterogeneity of variances, Wilcoxon test (non-parametrical) will be used to assess differences between case and controls. Convergent validity will not be tested since there is no Italian questionnaire available for comparison. The internal consistency - the strength of association among items will be tested using Cronbach's Alpha. Cases will be given the questionnaire at baseline and two week later to evaluate the test-retest reliability. The test-retest reliability analysis will be aimed to determine the questionnaire's reproducibility over time. The degree of concordance/agreement will be measured with Cohen's Kappa. In addition, the absolute agreement of test-retest results of different individuals will be tested with the intraclass correlation coefficient (ICC).

Statistical analysis will be performed with JMP 7.0 (SAS, Cary, USA). Where ratings will be missing, items will be excluded from the analysis pool. Patients who will not complete the questionnaire both at baseline and at the test-retest visit will be excluded from the analyses. A p<0.05 will be considered as significant.