The Relevance Of Serum Aquaporin-4Antibody Levels With The Clinical Features Of Neuromyelitis Optica Spectrum Disorders

ObjectiveTo detect the aquaporin-4(AQP-4) antibody in patients suffering from the acute longitudinally extensive transverse myelitis (LETM) and neuromyelitis optica(NMO). To investigate the correlation between AQP-4antibody titres and clinical characteristics. To analyse the association the antibody titers and disease activity and. prognosis. To provide clinical evidence for the pathogenicity of AQP-4antibody in NMOSD.MethodsTo perform quantitative detection to the sera AQP-4antibody of72idiopathic LETM and the78NMO patients in our hospital by immunofluorescent precipitation assay (FIPA). To retrospectively investigate the clinical manifestation and magnetic resonance imaging (MRI) feature. The disability severity in NMOSDs was assessed by the Expanded Disability Status Scale (EDSS). Magnetic resonance imaging (MRI) was performed to assess the involved lesions. The Spearman’s rank correlation was used as appropriate data analysis. In the seropositive LETM patients, we evaluated the correlation between AQP-4antibody titers and clinical parameters such as EDSS scores(at first episode and at last follow-up), number of segments of spinal cord involved, the interval period to next relapse and the conversion period of LETM to NMO. In patients with NMO, the correlation between AQP-4antibody titers and clinical parameters such as EDSS scores(at acute stage), number of segments of spinal cord involved and brain lesions count on MRI, the interval period to next relapse was analysed.Results1. The positivity for AQP4-Ab in patients with idiopathic LETM was68%.2.By Spearman analysis,we found that EDSS scores(at acute stage and at lastfollow-up), number of segments of spinal cord involved were positively correlated to AQP-4antibody levels (r=0.463,P=0.001; r=0.424,P=0.003;r=0.142, P=0.039). However, the sera AQP-4antibody level was not correlated with the time to next attack and the conversion time of LETM to NMO(r=-0.29, P=0.073; r=-0.141, P=0.458).3. Among the78patients suffering form NMO, the seropositivity rate of sera AQP-4antibody was73.1%.4. By Spearman analysis, it was obvious that EDSS scores at acute stage, number of segments of spinal cord involved and brain MRI lesions were positively correlated to AQP-4antibody levels (r=0.423, P=0.0001; r=0.355, P=0.002; r=0.286, P=0.022). But the sera AQP-4antibody level did not correlate with the interval period to the next attack(r=0.126,P=0.532).Conclusions1. Among the78NMO patients and the49AQP-4Ab positive patients with first-ever LETM, the result proved that serum AQP4antibody levels positively correlated with EDSS scores at acute stage, else the number of segments of spinal cord involved. It indicated that the AQP-4antibody titres in acute phase can point the severity and the activity of disease and the AQP-4antibody may involve in the pathopoiesis in NMO.2. The EDSS scores at last visit, were also associated with the AQP-4antibody levels at first episode in sero-positive LETM. The positive correlation indicated that NMO-IgG antibodies were useful to predict the final disability.3. The number of brain lesions were positively associated with the titres of AQP-4antibody in NMO patients. It was possible that AQP-4antibody played an important role in the formation of brain lesions.4. In seropositive LETM, the interval period to the next attack and the conversion period of LETM to NMO were not related with AQP-4antibody levels. In NMO patients, the sera AQP-4antibody level in acute phase lacked the statistical correlation with the interval period to the next attack. It suggested that the single AQP-4antibody status may not have predictive value for the relapse and conversion.