Cross-Cultural Translation and Validation of the Crohn's Anal Fistula Quality of Life Scale in Patients With Active Perianal Fistulizing Crohn's Disease

BACKGROUND: The Crohn's Anal Fistula Quality of Life scale was recently developed as the first disease-specific patient-reported outcome measure for patients with perianal fistulizing Crohn's disease. After crosscultural validation, the Crohn's Anal Fistula Quality of Life scale may be implemented internationally to measure the quality of life among patients with perianal fistulizing Crohn's disease. OBJECTIVE: To translate and validate the Crohn's Anal Fistula Quality of Life scale in Dutch patients with active perianal fistulizing Crohn's disease. STUDY DESIGN: Prospective observational cohort study. SETTING: Forty-one Dutch academic and nonacademic hospitals. PATIENTS: Patients with active perianal fistulizing Crohn's disease who completed all quality of Life questionnaires at the time of inclusion. MAIN OUTCOME MEASURES: Construct validity, internal consistency, test-retest reliability, and responsiveness of the Crohn's Anal Fistula Quality of Life scale. Item response theory was used to investigate individual properties of the Crohn's Anal Fistula Quality of Life scale, and differential item functioning for age, sex, and educational level was tested. RESULTS: Questionnaires were completed by 263 of 403 patients (response rate 65.3%). Evaluation of the construct validity showed a moderate correlation with the short IBD Questionnaire (r = -0.61) and EuroQol 5 Dimension 5 Level Questionnaire (r = -0.58 [utility], r = -0.42 [visual analog scale]). Overall internal consistency (Cronbach's alpha) was 0.93. Test-retest reliability was high (intraclass correlation coefficient 0.89). Responsiveness was reported in both improved and worsened perianal fistulizing Crohn's disease (p < 0.01). Item response theory analyses identified that the majority of the questions (72.7%) have moderate-to-high discrimination in predicting quality of life. No differential item functioning with clinical impact was identified. LIMITATIONS: Potential selection bias of respondents to questionnaires, the absence of a clinical criterion standard for assessing fistula status, and a relatively small sample size for the test-retest reliability analysis. CONCLUSIONS: In this prospective multicenter study, the Crohn's Anal Fistula Quality of Life scale was validated as a robust tool for measuring quality of life among patients with active perianal fistulizing Crohn's disease. In addition, this cross-cultural validation facilitates broader international implementation and future adaptations into other languages and cultural contexts. Further studies are required to define a minimal (clinically) important difference and/or minimal detectable change on the Crohn's Anal Fistula Quality of Life scale to measure treatment effects