Objective: To develop an epidemiological model of manifest Huntington’s disease (HD) to estimate international HD diagnosed prevalence by Shoulson–Fahn Total Functional Capacity (TFC)-based Stage based on diagnosed incidence rates and survival time.

Background: HD is a rare genetic, progressive, neurodegenerative disease. Reported prevalence rates are heterogeneous and likely underestimated, since many HD cases are not diagnosed due to unawareness of at-risk status, unavailability of genetic testing or social stigma. Accurate epidemiology estimates are important to ensure optimal access to care for individuals with HD.

Method: The model included several of the most populous countries with predominantly Western European ancestry (Brazil, Canada, France, Germany, Italy, Spain, UK, US). The annual number of diagnosed incident patients in each country was estimated by applying incidence rates identified in a review of the published literature to the total population. Distribution of incident patients by stage, and annual probabilities of progression and mortality by TFC-based stage were estimated from data in ENROLL-HD, a longitudinal, observational, multinational study of HD-affected individuals. For each country, the progression of annual incident cohorts was simulated over a 70-year period by applying these probabilities, which were assumed invariant across geographies. Annual diagnosed prevalence estimates by stage were obtained by summing the number of simulated patients alive in the model in each stage per year.

Results: The model estimates that there are around 70,000 prevalent diagnosed individuals with manifest HD in the selected countries, of which 75% are in TFC-based Stages 1 and 2. This equates to a diagnosed prevalence rate of 8.7, 9.5 and 3.5 per 100,000 in North America, Europe, and Brazil, respectively. The wide range of modelled diagnosed prevalence in sensitivity analyses (54,000 to 99,000) highlights the high uncertainty around HD epidemiological estimates.

Conclusion: This analysis contributes to the better characterization of HD epidemiology and highlights areas of uncertainty. Should disease-modifying therapies become available, increased awareness and optimism may lead to higher diagnosis rates. Health systems must be prepared and resourced for potential future increases in diagnosed prevalence, so that as many individuals as possible with HD can benefit from innovative therapies.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/modelling-huntingtons-disease-diagnosed-prevalence-from-diagnosed-incidence-and-survival-time/