Evaluation of ethnicity as a predictor of diagnostic phenotype and prognosis in neuromyelitis optica spectrum disorder in Toronto, Canada.

Background: Recent international studies suggest that ethnicity may predict relapse types and outcomes in NMOSD. Our aim was to evaluate ethnicity as a predictor of diagnostic phenotype and prognosis in a multi-ethnic NMOSD cohort from a single geographic region.

Methods: This was a multi-centre retrospective cohort study of NMOSD subjects in Toronto, Canada. Ethnicity was classified as Asian, black, Caucasian, and other. Regression models were used to assess the relationship between ethnicity and each of diagnostic phenotype (2006 vs. only 2015 diagnostic criteria), annualized relapse rate, and EDSS at last follow-up.

Results: Out of 81 patients with NMOSD, 87.7% were female, 70.4% positive for aquaporin-4 (AQP4) IgG, with mean age of onset 38.9 (17) years and median disease duration [IQR] of 9.8 [4.50, 16.59] years. Blacks compared to Asians were less likely to exhibit classic NMO as per 2006 diagnostic criteria (p = 0.006). Caucasians, compared to Asians, had lower EDSS scores at last follow-up (p = 0.008) despite a trend towards higher annualized relapse rates. Older age of onset was significantly associated with greater disability as measured by the EDSS (p = 0.003).

Conclusions: In this multi-ethnic cohort from Toronto, Canada, blacks with NMOSD were less likely than Asians to demonstrate classic NMO by 2006 diagnostic criteria. Caucasians had better long-term disability outcomes compared to Asians as measured by the EDSS.