Anderson-Fabry disease (FD) is a rare X-linked inherited lysosomal disease caused by reduced activity α-galactosidase A. Due to the heterogeneity of disease presentation and evolution, patient-reported outcome (PRO) tools, such as SF-36, do not provide accurate insights into patients’daily lives and impact of specific treatments. In response to the“Shared Clinical Decision Making”report published by the French Authority for Health, we aimed to construct a validated and FD-specific tool to appraise patients’needs and expectations towards their treatment. This endeavor was led with the help of French patient associations (APMF & VML) and dedicated expert centers. The Questionnaire of the Expectations of Patients with Fabry Disease with respect to their treatment (PNQ Fabry) was developed according tothe FDA/EMA method ologies and best practices for the development of PRO tools in rare diseases. Our approach comprised of 3 steps, as follows: concept elicitation and item generation, item reduction(quantitative survey), and final validation of the questionnaire through a 2-stage survey. Intrinsic and extrinsic stability of the PNQ Fabry was established, using a validated benchmark questionnaire. With the invaluable help of patient associations, we recruited a satisfactory population in this rare disease setting, to ensure robust participation to validate our PNQ (final number of questionnaires: 76).At the end of the process, we obtained a 26-item patient-reported questionnaire with excellent psychometric properties, exhibiting very satisfactory measurement outcomes for reliability and validity. The results of this initiative demonstrate that the PNQ Fabry is both acceptable to patients and accurate, as it addresses themes identified from patient interviews, that were further validated through statistical analyses of qualitative and quantitative surveys. An ongoing phase IV study is using this tool we believe it could be reliable and insightful in daily practice, to improve patient management in FD.
