The epidemiology and clinical presentation of seropositive neuromyelitis optica spectrum disorder in a US population

Abstract Objective To define the epidemiology and clinical presentation of seropositive neuromyelitis optica spectrum disorder (NMOSD) in a large US health system. Methods We completed a retrospective observational study of adult patients in the University of Colorado Health System from 1 January 2011 to 31 December 2020, using Health Data Compass (HDC), a data warehouse that combines electronic health information with claims and public health data in Colorado. We screened HDC for patients with either (1) an abnormal aquaporin‐4 IgG test or (2) any G36 ICD‐10 code. We extracted key clinical elements by chart review and confirmed diagnosis by the 2015 International Panel for NMO Diagnosis criteria. Annual incidence and prevalence rates were calculated. Results Our population consisted of 2,475,591 individuals contributing 11,103,522.72 person‐years of observation. In total, 115 seropositive NMOSD patients were identified. The average yearly incidence was 0.22 per 100,000 person‐years. Age and sex‐adjusted prevalence (per 100,000) was 4.33, and highest among those identifying as Asian or Pacific Islander (17.72), and Black (14.74), as separately by Hispanic ethnicity (8.02). Prevalence was higher in women (6.20:1 female:male ratio). Transverse myelitis (45%) and optic neuritis (43%) were the most common presenting clinical syndromes. In total, 6% of initial presentations were characterized by short‐segment transverse myelitis without other features. Interpretation Seropositive NMOSD incidence is higher in our cohort than many contemporary studies. Women and those identifying as Asian or Pacific Islander, Black, and Hispanic shoulder the highest burden of disease. Clinical onset with short‐segment myelitis underscores the need for serum aquaporin‐4 IgG testing in acute myelitis presentations.