The international panel for neuromyelitis optica (NMO) diagnosis has proposed diagnostic criteria for neuromyelitis optica spectrum disorders (NMOSD).

We assessed the impact of these criteria on diagnostic rates in a large cohort of patients.

We identified and applied the 2006 and 2015 criteria to all patients (n = 176) seen in the NMO and non-multiple sclerosis central nervous system demyelination clinic (part of the UK NMO service) from January 2013 to May 2015.

The 2006 criteria classified 63 of 176 (36%) patients as NMO. A total of 42 patients (67%) were aquaporin 4 (AQP4) immunoglobulin G (IgG) +ve and 21 (33%) AQP4 IgG –ve. The 2015 criteria classified 111 of 176 (63%) patients as NMOSD, of which 81 (73%) were AQP4 IgG +ve and 30 (27%) were AQP4 IgG –ve. There was an increase of 48 patients (76%) diagnosed as NMOSD using the new criteria.

Application of the 2015 criteria led to a rise in diagnosis of NMOSD by 76%. The rise in the AQP4 IgG +ve group contributed 62% and the seronegative group contributed 14%.