OBJECTIVES:

Spinal muscular atrophy (SMA) is a rare autosomal recessive neuromuscular disease that causes progressive proximal muscle weakness and paralysis. Recently nusinersen became the first treatment approved for patients with SMA. This study was designed to address gaps in the evidence regarding the impact on health-related quality of life (HRQL). These data are required for assessing cost-effectiveness of treatments, but capturing this in rare paediatric diseases is challenging.

METHODS:

Case histories were developed to match the definition of states in a decision model designed to measure the cost-effectiveness of nusinersen for the treatment of SMA type 1 and 2. The case studies were developed from a review of the literature focusing on HRQL impact, and interviews with five clinical experts in SMA. Following this, five clinical experts provided a proxy assessment of the case studies using the EQ-5D-Y and PedsQL-NMM (baseline states only).

RESULTS:

The experts who took part in the valuation interviews had an average of 14 years experience working with SMA patients. The SMA type 1 utilities ranged from -0.37 (requires ventilation) to 0.72 (reclassified as type 3), with quite substantial differences between some states. Most type 1 states had a utility score below zero indicating a state worse than dead. The SMA type 2 utilities ranged from -0.13 (worsened) to 0.77 (stands/walks unaided). The results showed an incremental increase of 0.03 moving from baseline (0.04) to mild improvement (0.07), and from mild to moderate improvement (0.10), and a large increase in utility values for the standing/walking states (0.53 and 0.77).

CONCLUSIONS:

The utility scores obtained in this study highlight the very substantial burden experienced by SMA patients. Despite the limitations in the methods used, this study produced data with face validity and is a useful starting point for understanding the burden of SMA type 1 and 2.