In our adult cohort presenting with a clinically isolated syndrome, particularly optic neuritis, we tested for MOG-Ab when there was diagnostic uncertainty or when we applied the McDonald MS diagnostic criteria,10 which requires the exclusion of alternative diagnoses; this approach aligns with general recommendations to test for MOG-Ab in patients with optic neuritis.11 Both the MS criteria and MOGAD criteria require exclusion of the other's diagnosis before their own application. Here, MOG is linked to optic neuritis.