Early Steps Towards a Huntington's Disease Burden-of-Illness Model: Estimating Out-of-Pocket Costs for Patients Showing Clinical Symptoms

OBJECTIVES: We aim to quantify illness-related out-of-pocket spending in persons with Huntington’s disease (PwHD) and their companions. The analysis is restricted to the subpopulation of PwHD’s living in the United States and achieving a UHDRS Diagnostic Confidence Level of 4 (DCL = 4; Stage 2 or 3 classification based on the HD Integrated Staging System [1,2]).

METHODS: The HD-Charge study surveyed 233 individuals to quantify indirect costs related to their own or a loved one’s HD [3]. PwHD’s were classified into Early, Middle, and Late stages according to their Total Functional Capacity (TFC). However, much of HD-Charge was conducted during the COVID-19 pandemic, potentially leading to biased results. Out-of-pocket expenditures from HD-Charge were used as the response variable in a generalized linear mixed model to estimate spending based on expense type, the PwHD’s TFC-based stage, and whether the costs were paid for by the PwHD or their companion. Costs were assumed to be Tweedie-distributed [5], and uncertainties in our estimates were quantified via parametric bootstrapping. Bias due to the COVID-19 pandemic was accounted for by leveraging external data from the University of Oxford’s COVID-19 Government Response Tracker [4].

RESULTS: An Early-stage PwHD/companion dyad was estimated to spend over $5,000 USD/year on HD-related out-of-pocket costs. Late-stage dyads spent significantly more at over $16,000 USD/year. Subject to assumptions discussed in the main work, these results remain valid in spite of the COVID-19 pandemic.

CONCLUSIONS: There are significant out-of-pocket costs associated with HD for PwHD’s and their companions. Quantifying these costs is an important first step in the development of a comprehensive burden-of-illness model, and could inform more accurate HEOR-based research related to HD.