Preferences and Utilities for Treatment Attributes in Type 2 and Non-ambulatory Type 3 Spinal Muscular Atrophy in the United Kingdom

Background: Spinal muscular atrophy (SMA) is a rare neuromuscular disease that affects motor neurons, resulting in progressive skeletal muscle weakness and atrophy.

Objective: The aim was to understand the value patients with SMA and caregivers place on treatment attributes and to estimate health utilities for SMA treatment outcomes from a general public sample.

Methods: Two discrete choice experiments were designed to elicit treatment preferences and health utilities, respectively. Patients with Type 2 and non-ambulatory Type 3 SMA, caregivers of patients with SMA and a general public sample in the UK completed the surveys. Patients and caregiver participants were recruited through patient associations. General public participants were recruited via a survey recruitment panel. Attributes included motor function, breathing function, treatment administration, treatment reactions, eyesight monitoring, contraception (patients only) and overall survival (general public only). Clustered conditional logit models were used to estimate treatment preferences, and marginal rates of substitution were used to estimate disutilities.

Results: Adult patients (n = 84) were twice as likely to choose a treatment with improved (vs. stable) motor and breathing function and four to five times less likely to choose a treatment with deteriorated (vs. stable) motor and breathing function as a treatment outcome. Caregivers (n = 83) were three to nine times more likely to choose improved and two to four times less likely to choose deteriorated (vs. stable) motor and breathing function. Both patients and caregivers preferred oral over intrathecal treatment. Treatment reactions, eyesight monitoring or contraception had no significant effect on patient choices. Conversely, caregivers preferred avoidance of treatment reactions. General public data (n = 506) yielded disutilities for unable to sit (- 0.408), need for > 16 h daily mechanical breathing support (- 0.304) and intrathecal therapy (- 0.071).

Conclusions: Study results show the importance of motor and breathing function to patients and caregivers, and an oral treatment preference. Disutilities (decrements to utility) were substantial for SMA disease outcomes and care aspects.