Incidence and prevalence of NMOSD in Australia and New Zealand

Objectives We have undertaken a clinic-based survey of neuromyelitis optica spectrum disorders (NMOSDs) in Australia and New Zealand to establish incidence and prevalence across the region and in populations of differing ancestry. Background NMOSD is a recently defined demyelinating disease of the central nervous system (CNS). The incidence and prevalence of NMOSD in Australia and New Zealand has not been established. Methods Centres managing patients with demyelinating disease of the CNS across Australia and New Zealand reported patients with clinical and laboratory features that were suspicious for NMOSD. Testing for aquaporin 4 antibodies was undertaken in all suspected cases. From this group, cases were identified who fulfilled the 2015 Wingerchuk diagnostic criteria for NMOSD. A capture–recapture methodology was used to estimate incidence and prevalence, based on additional laboratory identified cases. Results NMOSD was confirmed in 81/170 (48%) cases referred. Capture–recapture analysis gave an adjusted incidence estimate of 0.37 (95% CI 0.35 to 0.39) per million per year and a prevalence estimate for NMOSD of 0.70 (95% CI 0.61 to 0.78) per 100 000. NMOSD was three times more common in the Asian population (1.57 (95% CI 1.15 to 1.98) per 100 000) compared with the remainder of the population (0.57 (95% CI 0.50 to 0.65) per 100 000). The latitudinal gradient evident in multiple sclerosis was not seen in NMOSD. Conclusions NMOSD incidence and prevalence in Australia and New Zealand are comparable with figures from other populations of largely European ancestry. We found NMOSD to be more common in the population with Asian ancestry.</p

NMOSD and MS prevalence in the Indigenous populations of Australia and New Zealand

Background We studied the prevalence of neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) in Indigenous populations of Australia and New Zealand with the aim of assessing potential differences. Methods Cases of possible NMOSD and MS were collected from Australia and New Zealand. Clinical details, MR imaging, and serologic results were used to apply 2015 IPND diagnostic criteria for NMOSD and 2010 McDonald criteria for MS. Frequencies of self-determined ethnic ancestry were calculated for confirmed NMOSD, suspected NMOSD, and MS. Prevalence rates for NMOSD and MS according to ancestry were compared. Results There were 75 cases with NMOSD, 89 with suspected NMSOD, and 101 with MS. NMOSD cases were more likely to have Asian, Indigenous, or Other ancestry compared to suspected NMOSD or MS. There were no differences in the clinical phenotype of NMOSD seen in Indigenous compared to European ancestry populations. Per 100,000, the prevalence estimate for NMOSD in people with Māori ancestry was 1.50 (95% CI 0.52–2.49) which was similar to those with Asian ancestry 1.57 (95% CI 1.15–1.98). NMOSD prevalence in Australian Aboriginal and Torres Strait Islander populations was 0.38 (95% CI 0.00–0.80) per 100,000. Conclusion The prevalence of NMOSD in the Māori population is similar to South East Asian countries, reflecting their historical origins. The prevalence of MS in this group is intermediate between those with South East Asian and European ancestry living in New Zealand. Both NMOSD and particularly MS appear to be uncommon in the Indigenous populations of Australia