BACKGROUND: Neuromyelitis optica spectrum disorder (NMOSD) can be categorised into aquaporin-4 antibody (AQP4-IgG) NMOSD or seronegative NMOSD. While our knowledge of AQP4-IgG NMOSD has evolved significantly in the past decade, seronegative NMOSD remains less understood. This study aimed to evaluate the predictors of relapses and treatment responses in AQP4-IgG NMOSD and seronegative NMOSD. METHODS: This was a multicentre, international, retrospective cohort study using the MSBase registry. Recurrent relapse risk was assessed using an Andersen-Gill model and risk of first relapse was evaluated using a Cox proportional hazards model. Covariates that putatively influence relapse risk included demographic factors, clinical characteristics and immunosuppressive therapies; the latter was assessed as a time-varying covariate. RESULTS: A total of 398 patients (246 AQP4-IgG NMOSD and 152 seronegative NMOSD) were included. The AQP4-IgG NMOSD and seronegative NMOSD patients did not significantly differ by age at disease onset, ethnicity or annualised relapse rate. Both low-efficacy and high-efficacy immunosuppressive therapies were associated with significant reductions in recurrent relapse risk, with notably greater protection conferred by high-efficacy therapies in both AQP4-IgG NMOSD (HR 0.27, 95% CI 0.15 to 0.49, p<0.001) and seronegative NMOSD (HR 0.21, 95% CI 0.08 to 0.51, p<0.001). Longer disease duration (HR 0.97, 95% CI 0.95 to 0.99, p<0.001) and male sex (HR 0.52, 95% CI 0.34 to 0.84, p=0.007) were additional protective variables in reducing the recurrent relapse risk for the AQP4-IgG NMOSD group. CONCLUSION: Although further studies are needed to improve our understanding of seronegative NMOSD, our findings underscore the importance of aggressive treatment with high-efficacy immunotherapies in both NMOSD subtypes, regardless of serostatus.

Alfred Health Department of Neurology Melbourne Victoria Australia

American University of Beirut Beirut Lebanon

Bakirkoy Education and Research Hospital for Psychiatric and Neurological Diseases Istanbul Turkey

Biocruces Bizkaia Health Research Institute Barakaldo Spain

College of Medicine and Health Sciences and Sultan Qaboos University Hospital Sultan Qaboos University Al Khodh Oman

Department of Biotechnological and Applied Clinical Sciences University of L'Aquila L'Aquila Italy

Department of Medicine CORe University of Melbourne Melbourne Victoria Australia

Department of Neurology and Center of Clinical Neuroscience 1st Faculty of Medicine Charles University Prague and General University Hospital Prague Czech Republic

Department of Neurology Haydarpasa Numune Training and Research Hospital Istanbul Turkey

Department of Neurology Royal Brisbane Hospital Brisbane Queensland Australia

Department of Neurology Royal Melbourne Hospital Melbourne Victoria Australia

Department of Neurology School of Medicine and Koc University Research Center for Translational Medicine Istanbul Turkey

Department of Neurology Semmelweis University Budapest Hungary

Department of Neurology Universitair Ziekenhuis Gent Gent Belgium

Department of Neurology University of Debrecen Debrecen Hungary

Department of Neuroscience MS Center Neurology Unit S Maria delle Croci Hospital Ravenna Italy

Department of Neuroscience S Maria delle Croci Hospital Ravenna Italy

Department of Neuroscience School of Translational Medicine Monash University Melbourne Victoria Australia

Division of Neurology Department of Medicine Amiri Hospital Kuwait City Kuwait

Faculty of Medicine and Health Sciences Translational Neurosciences Research Group University of Antwerp Wilrijk Belgium

Faculty of Medicine Isfahan University of Medical sciences Isfahan Iran

Hunter Medical Research Institute The University of Newcastle Newcastle New South Wales Australia

Hunter New England Health John Hunter Hospital New Lambton Heights New South Wales Australia

Izmir University of Economics Medical Point Hospital İzmir Turkey

Multiple Sclerosis Research Association Izmir Turkey

Multiple Sclerosis Unit AOU Policlinico G Rodolico San Marco University of Catania Catania Italy

Nehme and Therese Tohme Multiple Sclerosis Center American University of Beirut Medical Center Beirut Lebanon

Neurology Department Harley Street Medical Centre Abu Dhabi UAE

Neurology Dr Etemadifar MS Institute Isfahan Iran

Neurology Galdakao Usanosolo University Hospital Osakidetza Basque Health Service Galdakao Spain

Neurology Royal Hobart Hospital Hobart Tasmania Australia

Neurology Universitair Ziekenhuis Antwerpen Edegem Belgium

Neurology Walton Centre for Neurology and Neurosurgery Liverpool UK

Neuroscience Department of Surgical and Medical Sciences and Advanced Technologies 'G F Ingrassia' University of Catania Catania Italy

The University of Queensland Brisbane Queensland Australia

References provided by Crossref.org

Progression independent of relapse activity and relapse-associated worsening in seronegative NMOSD: an international cohort study