New models may better assess impact of AADC deficiency: Study
Mathematical models may also be used to evaluate value of new treatments
Through a series of interviews with doctors, caregivers, and members of the general public, scientists have calculated new health state utilities (HSUs) that can be used to make economic assessments about the impact of AADC deficiency on a patient’s quality of life.
“The HSUs generated here reflect an accurate representation of the burden and impact of [AADC deficiency] on [health-related quality of life] and can be used in economic evaluations of new treatments in [AADC deficiency],” researchers wrote in the study “Estimating health state utilities for aromatic L-amino acid decarboxylase deficiency (AADCd) in the United States,” which was published in Health and Quality of Life Outcomes.
The work was funded by PTC Therapeutics, the company that sells Kebilidi (eladocagene exuparvovec-tneq), a gene therapy for AADC deficiency that was conditionally approved in the U.S. last year. The therapy is also available in the U.K. and the European Union, where it’s sold as Upstaza.
Symptoms include impaired mobility, problems with communication
AADC deficiency is a genetic disorder characterized by symptoms including impaired mobility and problems with communication. In the absence of treatment, many patients have little ability to move their body or communicate their needs. Kebilidi recently became the first approved treatment to help ease symptoms of AADC deficiency by addressing the root cause of the disease.
Figuring out pricing and other economic considerations for life-changing medicines like Kebilidi is complicated in part because it’s impossible to put an objective price on the value of being able to sit up or walk. HSUs work to ascribe numerical quantities to different functional statuses, which can help inform these analyses.
In the study, researchers set out to create HSUs for AADC deficiency. To do this, they first talked to a group of doctors and caregivers to create several vignettes representing different manifestations of AADC deficiency. For example, one vignette described a patient who was unable to get out of bed, whereas another described a patient who could sit up unassisted.
Then, the researchers conducted a series of interviews with more than 100 members of the general public. Participants were faced with the various vignettes and basically asked to rate how much less time they’d be wiling to live in exchange for having more functionality. This is called a time trade-off (TTO) approach.
“The TTO approach generates utility weights that could be used in economic analyses to measure and compare health gains using different therapies,” the researchers wrote.
As expected, the numbers generally reflected more acceptance of states with more functionality. Participants were generally quite willing to give up years of hypothetical lifespan in exchange for being able to walk around, for example.
“The range in values from the most to least severe health state illustrates the devastation of the disease at its most severe, as well as the significant impact on quality of life when a health state is improved, suggestive of the potential for effective treatments to substantially improve [health-related quality of life] in these patients,” the researchers concluded.
The team noted that these mathematical models may be useful in future evaluations to assess the value of Kebilidi and other treatments for AADC deficiency.
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