Background: Fabry disease is rare and multisystemic, necessitating a disease-specific quality of life scale to assess changes in quality of life. We developed the Adult Fabry Disease Quality of Life scale to measure the quality of life of adult patients with Fabry disease. Objectives: To confirm the reliability of the Adult Fabry Disease Quality of Life scale using the test–retest method and calculate the minimal important change. Design: This study was based on two questionnaire surveys conducted at approximately 2-week intervals in November and December 2024 in Japan. Methods: Twenty-eight participants completed questionnaires consisting of background information, the Adult Fabry Disease Quality of Life scale, and the Short Form-8. In the second survey, an anchor question with a 7-point Likert scale was added to assess changes in general health. The intraclass correlation coefficient for reliability and Cronbach’s alpha coefficient for internal consistency were calculated. For minimal important changes, the average value of the smallest change group for the anchor question was calculated. Results: The intraclass correlation coefficients for each factor and the total score on the Adult Fabry Disease Quality of Life scale were 0.892–0.946. Cronbach’s alpha coefficient was 0.948 for the first survey and 0.956 for the second. In response to the anchor question, three participants (13.0%) felt a little worse, and three (13.0%) felt a little better. Those who felt a little worse and those who felt a little better showed improvements in quality of life of 3.7 and 5.3 points, respectively. Conclusion: The Adult Fabry Disease Quality of Life scale is highly reproducible at 2-week intervals. Defining the minimum important change was not possible, which is important when used as an outcome. Future studies should establish it using the anchor method. Trial Registration: This prospective study was registered with the UMIN-CTR on September 1, 2024 (No. UMIN000055144).
Koto et al. (Sun,) studied this question.