AQP4 and Autoimmunity: The most sensitive diagnostic factors for middle-aged and elderly-onset AQP4-ON were ‘unilateral involvement’ (sensitivity 0.88), ‘unilateral involvement or neurological history’ (sensitivity 0.91), and ‘unilateral involvement or other autoimmune antibodies’ (sensitivity 1.00), and the most specific factor was neurological history (specificity 0.98).