Transatlantic confusion in MS diagnostic criteria: one patient, two continents, zero diagnosis

The lack of universal diagnostic criteria for multiple sclerosis (MS) delays diagnosis and care. Diagnostic guidelines widen existing gaps in neurological health depending on how they are applied by clinicians across the globe. The 2016 MAGNIMS and 2017 McDonald's criteria for MS exclude cerebrospinal fluid (CSF) findings, and optic neuritis (ON), respectively, opening the door for missed diagnosis, which, in under-resourced settings, could have devastating consequences. When guidelines prioritize precision over clinical inclusion, they risk excluding patients with a true diagnosis, and undermine the very utility they aim to standardize. Diagnostic frameworks must evolve not only to reflect statistical rigor but support health policy that demands the real-world consequences of underdiagnosis just as heavily as the cost of overdiagnosis. Precision with inclusivity and epidemiologic modeling should be part of that conversation. The burden of MS is immense; we need universal diagnostic criteria that cut across borders.