Objective: To determine the prognostic value of AQP4 antibody in the cohort of Chinese patients with neuromyelitis optical (NMO), HR-NMO (high-risk NMO)and classic multiple sclerosis (MS).

Methods: Sera of patients with NMO, HR-NMO and MS were all investigated for the presence of AQP4 antibody by indirect immunofluorescence in human AQP4-transfected cells. The diagnostic and prognostic values of anti-AQP4 antibody were evaluated in 352 patients with NMO (n=106), HR-NMO (n=84) including optico-spinal MS (OSMS), longitudinally extensive transverse myelitis (LETM), recurrent optic neuritis (RON) and optic neuritis (ON) or transverse myelitis (TM) with other autoimmune disease and classic MS (n=162). All patients were followed up at outpatient clinics or by telephone.

Results: In our study, the anti-AQP4 antibody's seropositivity in all demyelinating cases (n=352) was 31.3%. And 72 (65.5%) seropositive patients presented with severe ON, 82 (74.5%) with TM, 60 (54.4%) with spinal-cord lesion more than 3 segments, 16 (14.5%) had relapses of ON and 38 (34.5%) relapses of TM during a follow-up period of 24 months. Significant differences existed between anti-AQP4 antibody seropositivity and seronegative in terms of concurrent severe ON, TM, spinal-cord lesion more than 3 segments and relapses of ON and TM (P<0.05). Also, in NMO patient seropositive for anti-AQP4 antibody (n=78), 28 (35.9%) developed relapses of TM. However, in HR-NMO patient with seropositivity (n=28), 4 (14.3%) developed relapses of ON and 10 (35.7%) relapses of TM. The relapse of ON or TM occurred in 57/110 seropositive patients versus 17/242 seronegative ones (P<0.05).

Conclusions: As compared with anti-AQP4 antibody-negative ones, anti-AQP4 antibody-positive patients show significantly higher frequencies of severe ON, TM, longitudinal spinal-cord segments and they are more predisposed to ON or TM relapse. And seropositive NMO and HR-NMO patients are more likely to develop relapses of ON or TM. Anti-AQP4 antibody may play some roles in the diagnosis and prognostic predication of demyelinating diseases in central nervous system.