Elicitation of Health Utilities Online in Patients With Spinal Muscular Atrophy

OBJECTIVES: Spinal muscular atrophy (SMA) is a rare, genetically inherited, neuromuscular condition characterised by progressive muscle weakness and loss of movement. The aim of this study was to generate utility values in order to demonstrate the impact that this condition has on patients’ health-related quality of life and for use in economic cost-utility analyses.

METHODS: Participants, aged 18 to 67, were recruited by a third party (Qualtrics LLC) which maintains a series of online panel respondents. Participants responded to time trade-off (TTO), and standard gamble (SG) scenarios, as well as rating these scenarios with a visual analogue scale (VAS). Participants were presented with the health state vignettes and asked to imagine themselves as being a parent of the child described in the scenario. Four health state vignettes were presented to participants reflecting the health states in the economic model.

RESULTS: 321 participants completed the study: 160 females; 161 males and 1 who preferred not to provide their gender. The vignettes were rated as SWD as follows: 47.8% rated “permanent assisted ventilation” (PAV) as a SWD; 47.8% rated “non-sitting” as a SWD; 41.0% rated “sitting”; and 19.5% rated the “walking” state as a SWD. For the TTO, it may be seen that participants were not able to discriminate between the two most severe health states. Mean utilities increased as the health states became less severe with “walking” having the largest mean utility value. The differences were statistically significant overall (F(1,321) = 80.96, p<0.0001. Mean VAS utilities showed a linear increase across the health states. These differences were statistically significant (F(1,321) = 234.82, p<0.0001).

CONCLUSIONS: The mean utilities were broadly aligned with severity of the condition described, although participants did not distinguish between the “PAV” and “non-sitting”, whereas “sitting” and “walking” were rated higher than the other two.