Estimating the disutility of relapse in relapsing-remitting and secondary progressive multiple sclerosis using the EQ-5D-5L, AQoL-8D, EQ-5D-5L-psychosocial, and SF-6D: implications for health economic evaluation models.

Background And Aims: Relapses are an important clinical feature of multiple sclerosis (MS) that result in temporary negative changes in quality of life (QoL), measured by health state utilities (HSUs) (disutilities). We aimed to quantify disutilities of relapse in relapsing remitting MS (RRMS), secondary progressive MS (SPMS), and relapse onset MS [ROMS (including both RRMS and SPMS)] and examine these values by disability severity using four multi-attribute utility instruments (MAUIs).

Methods: We estimated (crude and adjusted and stratified by disability severity) disutilities (representing the mean difference in HSUs of 'relapse' and 'no relapse' groups as well as 'unsure' and 'no relapse' groups) in RRMS (n = 1056), SPMS (n = 239), and ROMS (n = 1295) cohorts from the Australian MS Longitudinal Study's 2020 QoL survey, using the EQ-5D-5L, AQoL-8D, EQ-5D-5L-Psychosocial, and SF-6D MAUIs.

Results: Adjusted mean overall disutilities of relapse in RMSS/SPMS/ROMS were - 0.101/- 0.149/- 0.129 (EQ-5D-5L), - 0.092/- 0.167/- 0.113 (AQoL-8D), - 0.080/- 0.139/- 0.097 (EQ-5D-5L-Psychosocial), and - 0.116/- 0.161/- 0.130 (SF-6D), approximately 1.5 times higher in SPMS than in RRMS, in all MAUI. All estimates were statistically significant and/or clinically meaningful. Adjusted disutilities of RRMS and ROMS demonstrated a U-shaped relationship between relapse disutilities and disability severity. Relapse disutilities were higher in 'severe' disability than 'mild' and 'moderate' in the SPMS cohort.

Conclusion: MS-related relapses are associated with substantial utility decrements. As the type and severity of MS influence disutility of relapse, the use of disability severity and MS-type-specific disutility inputs is recommended in future health economic evaluations of MS. Our study supports relapse management and prevention as major mechanisms to improve QoL in people with MS.