| Abstract Body | Introduction:
Neuromyelitis optica spectrum disorder (NMOSD) is a rare central nervous system autoimmune
condition where most patients harbour antibodies against aquaporin-4, however a minority are
seronegative. Whilst previous studies had identified predictors of relapses in AQP4-IgG NMOSD, a
scarcity of knowledge exists about the seronegative subtype.
Objectives/Aims:
The aim of this study is to characterise the demographic features and relapse risks in AQP4-IgG
NMOSD and seronegative NMOSD.
Methods:
This was a multi-centre, international cohort study using the MSBase database. Relapse risks were
assessed as risk of recurrent relapses using Andersen-Gill (AG) model and time to first relapse using
Cox proportional hazards model. The covariates included demographic factors, clinical characteristics
and treatment exposure. Treatment was assessed as a time-varying covariate and was categorised as
high-efficacy or low efficacy therapies, with multiple sclerosis therapies as reference.
Results:
A total of 398 patients were included in the study; 246 AQP4-IgG NMOSD patients followed up for a
median of 4.2 years and 152 seronegative NMOSD patients followed up for a median of 4.6 years.
Baseline demographic data were closely aligned between both groups. In the AG model, both high efficacy (mostly Rituximab) and low-efficacy (mostly azathioprine) therapies were associated with
relapse reduction. High-efficacy therapy was associated with the highest protection against recurrent
relapse risk in the AQP4-IgG NMOSD (HR 0.27, CI 0.15-0.49, p<0.001) and seronegative NMOSD (HR
0.21, CI 0.08-0.51, p<0.001) groups. In the AQP4-IgG NMOSD group, male sex (HR 0.52, CI 0.34-
0.84, p=0.007) and longer disease duration (HR 0.97, CI 0.95-0.99, p<0.001) were also protective.
Conclusion:
Our results highlight that regardless of antibody status, immunotherapies, particularly high-efficacy
immunotherapies, are exceedingly effective at controlling relapse risks.
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