Longitudinal evaluation of clinical characteristics of Chinese neuromyelitis optica spectrum disorder patients with different AQP4-IgG serostatus

Anti-aquaporin-4 antibody (AQP4-IgG) is a diagnostic marker of neuromyelitis optica spectrum disorder (NMOSD), but the relationship of different AQP4-IgG serostatus with clinical manifestations and recurrence of disease is still uncertain.We attempted to observe the changes of AQP4-IgG serostatus and the differences of corresponding clinical manifestations between AQP4-IgG-positive (AQP4-IgG+) and AQP4-IgG-negative (AQP4-IgG-) patients during 36-month follow-up, and to explore the significance of AQP4-IgG serostatus in the pathogenesis of NMOSD.The AQP4-IgG serostatus in eighty-four NMOSD patients during 36 months were re-checked regularly every 6 months in stable phase of the disease, and an additional AQP4-IgG test was performed when the disease relapsed. The clinical data were collected, including gender, age, clinical symptoms and signs, location and length of affected spinal cord segments, expanded disability status scale (EDSS), course of disease, annual recurrence rate (ARR), concomitant connective tissue disease (CTD) and other autoimmune antibodies. According to the change of AQP4-IgG serostatus during 36 months, the enrolled patients were divided into the various groups: with AQP4-IgG+ at the first diagnosis; with AQP4-IgG- at the first diagnosis; with persistent AQP4-IgG+; with persistent AQP4-IgG-; with conversion to AQP4-IgG-. The clinical characteristics of NMOSD patients among different groups were compared.Eighty-four NMOSD patients (12 males and 72 females) were included in this study. For the patients with AQP4-IgG+ at the first diagnosis (60 patients, 71.4%), there were 29 patients (48.3%) continuously positive; 31 cases (51.7%) turned positive to negative while 9 cases (29.0%) turned positive again in which 7 cases (77.8%) coincided with recurrence. The re-positive change of AQP4-IgG was significantly correlated with the recurrence of the disease (P < 0.05); for the patients with AQP4-IgG- at the first diagnosis (24 patients, 28.6%), 19 patients (79.2%) remained negative, and 5 patients (20.8%) turned negative to positive in which 1 patient (20.0%) had a relapse. This conversion of AQP4-IgG serostatus had no significant correlation with the recurrence of the disease (P > 0.05). There was no significant difference in clinical manifestations between the AQP4-IgG+ and AQP4-IgG- group at the diagnosis, or between the persistent AQP4-IgG+ and persistent AQP4-IgG- group during thirty-six months (P > 0.05). The patients with persistent AQP4-IgG+ was more likely to accompany with other antibodies than those with conversion to AQP4-IgG- (P < 0.05), while no significant differences were found in the gross clinical characteristics. (P > 0.05).AQP4-IgG serostatus can fluctuate in the different phase of NMOSD. There is no significant difference in clinical characteristics between AQP4-IgG+ and AQP4-IgG- patients. The conversion of AQP4-IgG+ to AQP4-IgG- may not be an appropriate target for treatment, but patients who are AQP4-IgG+ turn positive again after conversion to negative need to be vigilant for the recurrence of the disease.