To define the epidemiology and demographics of seropositive neuromyelitis optica spectrum disorder (NMOSD) in a large US health system.

Epidemiological studies of NMOSD have been limited by several factors. Challenges include disease rarity and identification, a heterogenous composition of individuals diagnosed with seronegative disease, and variable capture of the biomarker, aquaporin-4 antibodies, in large datasets. Health Data Compass (HDC), a data warehouse at the University of Colorado, combines health system data with claims, billing, and public health data in Colorado. Notably, HDC curates all forms of aquaporin-4 testing since it became clinically available.

This is a retrospective cohort study comprising all adult patients that had any contact with the University of Colorado Health System from 1/1/2011 to 12/31/2020. Through HDC, we extracted salient demographic information for the constituent population and our cohort of NMOSD patients. All database lab entries for aquaporin-4 were reviewed with HDC analysts to ensure accurate capture of seropositive patients. Prevalence and incidence were calculated yearly and for the total observation period. Diagnosis was confirmed by chart review using the IPND 2015 criteria. Statistical analysis was completed using SAS version 9.4.

Our population consisted of 2,475,591 individuals contributing 11,103,522.72 person-years of observation.115 seropositive NMOSD patients were identified. The average yearly incidence of diagnosis was 0.50 per 100,000 person-years (95% CI 0.38 – 0.65). Prevalence as of 12/31/20 was 4.65 per 100,000 (95% CI 3.80 – 5.49). Regarding prevalent NMOSD patients, 87% were female (6.7 F:M). 21.7% (N = 25) of NMOSD patients identified as Hispanic, 18.3% as Black (N = 21), 8.7% (N = 10) as Asian, 60.0% (N = 69) as White, and 8.7% (N = 10) as Other race.

We discovered a higher incidence rate of NMOSD than previous US studies. Our prevalence results are consistent with existing literature.