OBJECTIVES: Neuromyelitis optica spectrum disorder (NMOSD) is a rare, complement-mediated autoimmune disease that can be misdiagnosed for conditions with similar clinical presentations, such as multiple sclerosis (MS). Preventing NMOSD misdiagnosis is critical, as using certain MS medications in patients with NMOSD can exacerbate symptoms and lead to catastrophic disease activity. This study evaluated the incidence of NMOSD misdiagnosis and the utilization of medications that could exacerbate disease activity in patients with NMOSD.

METHODS: Data from the Magellan Health (medical/pharmacy) database between January 1, 2016 and December 31, 2021 were analyzed and pooled for patients with NMOSD (≥ 2 claims for NMOSD) and probable NMOSD (≥ 2 claims for NMOSD-related conditions: eg, optic neuritis and encephalomyelitis); a propensity score-matched control group was generated from all other member profiles. Outcomes included the most common diagnoses and overall medication use in the pre-index period (from January 1, 2016 to the first claim for NMOSD or probable NMOSD).

RESULTS: An equal number (10 679) of patients with NMOSD/probable NMOSD and of matched controls were identified. In both groups, the median age was 54.0 years, and 60.2% were female. In the pre-index period, patients with NMOSD or probable NMOSD had a significantly higher rate of diagnoses for conditions having similar clinical manifestations to NMOSD compared with the matched control group (42.0% vs 31.0%; P < 0.001), with the largest difference observed for MS diagnosis (10.1% vs 0.8%; P < 0.0001). Medications known to exacerbate NMOSD were found at significantly (P < 0.001) higher numbers in the NMOSD/probable NMOSD group compared with matched controls (81 vs 7 [interferon beta]; 57 vs 4 [natalizumab]; 44 vs 5 [fingolimod]).

CONCLUSIONS: Misdiagnoses and use of NMOSD-exacerbating medications are common in patients with NMOSD or probable NMOSD, which calls for earlier identification and appropriate disease management for patients with NMOSD.