Chronic hypoparathyroidism is a rare disease associated with an impaired quality of life. Recommendations suggest frequent monitoring of quality of life, but for French-speaking people, only generic scales are available despite the fact that chronic hypoparathyroidism has specific symptoms and impact. The aim of this study was to adapt and validate the French version of Hypoparathyroid Patient Questionnaire 28 (HPQ28), an already validated tool in patients living with chronic hypoparathyroidism, available in English and German. HPQ28 was translated and back-translated from English into French. Translations were harmonized with the original author. Assessment of psychometric properties of the French version of HPQ28 was performed in the ComPaRe-Epi-Hypo e-cohort, a nationwide cohort of adult patients living with chronic hypoparathyroidism in France. Internal consistency was evaluated using Cronbach's alpha. Dimensional validity was studied using confirmatory factor analysis (CFA). Construct validity compared the answers from the French version of HPQ28 with those from the EQ-5D-5L, EQ-5D-VAS, and MYMPO2 instruments. Reliability was evaluated by the intra-class correlation coefficient (ICC) of a test-retest within a 2-wk interval. Between August 2023 and August 2024, 183 patients completed HPQ28, EQ-5D, and MYMOP2 scales. The majority (92%) of the participants were women, with a median[IQR] age of 52[44
60]. Etiology of the disease was neck surgery and genetic abnormalities in 82% and 8% of cases, respectively. Internal consistency was good (Cronbach's alpha 0.93, 95% CI 0.91 to 0.94). CFA found a unidimensional structure of the questionnaire. Construct validity showed positive correlation with MYMOP2 (