Background: Individuals and/or caregivers of individuals affected by spinal muscular atrophy (SMA) completed the 2019 Cure SMA Community Update Survey, online, assessing health-related quality of life (HRQoL), loss of work productivity, and fatigue using the Health Utilities Index Questionnaire (HUI), the Work Productivity and Activity Impairment Questionnaire (WPAI), and the Patient Reported Outcomes Measurement Information System Fatigue Short Form (PROMIS Fatigue SF), respectively. The purpose was to collect baseline quality of life results among individuals affected by SMA using the above Patient Reported Outcome Measures (PROMs).
Results: Of 666 surveys completed between March and May 2019, 478 were included in this analysis, accounting for duplicates, missing data, or deaths. The breakdown across SMA type I, II and III was 25, 47 and 28%, respectively. Responses were characterized by current functional status/milestone, with subsets for "permanent ventilation," "non-sitters," "sitters," "walk with support," and "walk alone." WPAI and HUI respondents included affected adults and caregivers. The PROMIS Fatigue SF was completed by the primary caregiver of affected children. Overall, those affected by a less severe form of SMA and with a higher functional status reported higher HRQoL and lower work productivity and activity impairment. All affected individuals reported higher fatigue levels than the general population.
Conclusions: This study offers useful insights into the burden of SMA among affected individuals and their caregivers. The results provide a baseline picture of the patient and caregiver experience with SMA in a post-treatment era from which to measure year-over-year changes in quality of life scores from new therapies and improved care. The WPAI demonstrates the significant impact of work productivity among SMA populations. Aspects of the HUI seem more appropriate to certain SMA sub-populations than others. Measures from the PROMIS Fatigue SF appear to under-represent the burden of fatigue often reported by SMA individuals and caregivers; this may, perhaps be due to a lack of sensitivity in the questions associated with fatigue in the SMA affected population, when compared with other studies on this topic. Overall, these results suggest the need for SMA-specific quality of life outcome measures to fully capture clinically meaningful change in the SMA population.
Keywords: Health related quality of life; Health utilities index; PROMIS fatigue short form; Patient reported outcome measures; Spinal muscular atrophy; Work productivity and activity impairment.