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Anti AQP4 antibody status in Thai patients with demyelinating disorders

Objective: To determine anti-AQP4 antibody status in Thai patients with demyelinating diseases. Methods: Blood samples of patients visiting MS clinic at Siriraj Hospital, Thailand were collected and sent to Tohoku University for testing anti-AQP4 antibodies using AQP4-transfected cell-based assay. Diagnosis was as follows. Neuromyelitis optica (NMO) used NMO criteria 2006 except for presence of NMO IgG status. Optic-spinal MS (OSMS) was defined as optic neuritis (ON) and myelitis with no spinal cord magnetic resonance imaging (MRI) lesion over 3 vertebral bodies (VB) and normal brain MRI. High-risk NMO had either of (i) recurrent ON without brain lesion or (ii) myelitis with 3 VB involvement (with or without brain lesions) or (iii) ON and/or myelitis without 3 VB involvement with brain MRI compatible with NMO. Multiple Sclerosis (MS) was based on revised McDonald criteria 2005. Results: From 141 patients, 54 (38 %) had anti-AQP4 antibody positive. Anti-AQP4 antibody was found 18/23 (78.3%) in NMO and 12/33 (36.4%) in high-risk NMO patients. NMO-spectrum disorder (NMO/high risk NMO) with positive anti AQP4 antibody had higher female preference, equal or over 3 VB spinal cord involvement than MS patients with negative anti AQP4 antibody. Length of cord involvement was significantly greater in NMO spectrum disorder (P<0.0001). Brain MRI compatible with Barkhof criteria was not significantly different between the two groups. (P=0.066). Presence of cerebrospinal fluid (CSF) oligoclonal bands and CSF-WBC over 50 or neutrophils over 5 cell/mm3 were also not different (P=0.50). Among 54 anti AQP4 seropositive patients, 11 (20.4%) had MS. Four of 11 fulfilled McDonald criteria. Seven had never done spinal cord MRI, four from inaccessibility and 3 had symptoms other than spinal cord involvement. Another three had MRI spinal cord at remission therefore it is possible that spinal lesions had already resolved. The other one had brain MRI compatible with McDonald criteria and 2 VB spinal cord involvement. Therefore, a diagnosis of MS and not NMO was given. MRI with MS protocol, brain and whole spinal cord, at the time of acute relapse may help to differentiate between NMO spectrum disorder and MS without using anti AQP4 antibody. Conclusion: NMO spectrum disorder in Thai patients was similar to those from other countries. CMS diagnosis in our country may be given in NMO patients who had more brain lesions and/or spinal cord MRI was not perform at acute relapse.

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