A point-of-care diagnostic test for aquaporin-4 antibody seropositive neuromyelitis optica

Overview and Diagnostic Approach in Autoimmune Neurology

OBJECTIVE

The field of autoimmune neurology is rapidly evolving. This article reviews the epidemiology and pathophysiology as well as current approaches to clinical and paraclinical assessment, testing paradigms, and general principles of treatment.

LATEST DEVELOPMENTS

Improved recognition of autoimmune diagnoses among patients who have phenotypically diverse, subacute onset neurologic presentations is facilitated by disease-specific antibody biomarker discovery. These antibodies have varying associations with paraneoplastic causation (from no association to greater than 70% positive predictive value), immunotherapy responses, and outcomes. To simplify assessment in an increasingly complex discipline, neurologic phenotype-specific serum and CSF antibody evaluations are recommended. Clinical trials have led to the approval of monoclonal therapies for neuromyelitis optica spectrum disorder (NMOSD) and are underway for N-methyl-d-aspartate (NMDA) receptor and leucine-rich glioma inactivated protein 1 (LGI1) encephalitides.

ESSENTIAL POINTS

Autoimmune neurology is now a mainstream subspecialty, consisting of disorders with diverse presentations detectable using antibody testing of serum and CSF. Early and sustained immunotherapy (eg, corticosteroids, intravenous immunoglobulin [IVIg], plasma exchange) is recommended and may be supplemented by immune suppressants (eg, rituximab or cyclophosphamide) to sustain responses and optimize outcomes.

Predicting time to serologic diagnosis of AQP4+ NMOSD based on clinical factors and social determinants of health

BACKGROUND

Early serologic diagnosis and initiation of targeted therapy are associated with better outcomes in aquaporin-4 IgG positive (AQP4+) neuromyelitis optica spectrum disorder (NMOSD).

OBJECTIVE

To determine predictors of time to serologic diagnosis of AQP4+ NMOSD.

METHODS

In CANOPTICS, a multi-centre, Canadian cohort study of NMOSD, we retrospectively evaluated time from the first clinical attack to first positive AQP4-IgG serology. We used a multivariable negative binomial regression model to evaluate possible predictors of time to diagnosis.

RESULTS

We identified 129 participants with AQP4+ NMOSD from 7 centres. Diagnostic delay of >1 month was observed in 82 (63.6 %). Asian compared to European (White) ethnicity (IRR:0.40, 95 % CI:0.21-0.78), female sex (IRR:0.56, 95 % CI:0.32-0.99), later calendar year (IRR:0.84, 95 % CI:0.81-0.86), and hospitalization for the first attack (IRR:0.35, 95 % CI:0.20-0.62) were associated with shorter times to serologic diagnosis. We did not observe any overall effect of Afro-Caribbean ethnicity, but in exploratory analyses, Afro-Caribbean individuals with low income had longer times to diagnosis.

CONCLUSION

More than 60 % of patients with NMOSD experienced delays to AQP4-IgG serologic diagnosis in this cohort. Given evidence of more adverse long-term outcomes in Afro-Caribbean individuals with NMOSD, intersectional effects of ethnicity and social determinants of health merit further study.

Rectifying global inequities in neuromyelitis optica diagnosis and treatment

The standard of care for patients with neuromyelitis optica (NMO) has become highly unequal globally. Sufficient data have been published to demonstrate that NMO is a disabling-and at times, fatal-disease needing preventive immunosuppressive treatment. Since 2019, there are multiple regulatory authority-approved disease-modifying therapies (DMTs) for aquaporin-4 antibody seropositive NMO for patients. Reframing the picture of NMO globally is now needed. When considered as a disease of high mortality when left untreated, parallel programs to those for cancer, HIV/AIDS, or tuberculosis can be considered. Nine collective goals for rectifying global inequities in NMO diagnosis and treatment are proposed.