The 9 patients seropositive by cell-based IIFA while seronegative by tissue-based IIFA had NMO (3), RM with LETM (3), a single attack of LETM (1), relapsing ON (1) and a single ON attack (1). versus 22% by tissue-based IIFA (p = 1.000); however the differences were not statistically significant. All patients seropositive by tissue-based IIFA were also seropositive for AQP4 autoantibodies by cell-based IIFA. Among 29 NMOSD patients seropositive for AQP4 autoantibodies by cell-based IIFA, 20 (69%) were seropositive by tissue-based IIFA. The 9 patients seropositive by cell-based IIFA while seronegative by tissue-based IIFA had NMO (3), RM with LETM (3), a single attack of LETM (1), relapsing ON (1) and a single ON attack (1). Among 23 NMO or RM patients seropositive for AQP4 autoantibodies by cell-based IIFA, comparison between those seropositive (n = 17) and seronegative (n = 6) by tissue-based IIFA revealed no differences in clinical and neuroradiological characteristics between the two groups. Conclusion Cell-based IIFA is usually slightly more sensitive than tissue-based IIFA in detection of AQP4 autoantibodies, which are highly specific for NMOSD. Background Neuromyelitis optica (NMO) is usually a severe central nervous system inflammatory demyelinating disorder (CNS IDD) characterized by monophasic or relapsing optic neuritis (ON) and acute transverse myelitis (ATM) [1-6]. Relapsing NMO is the predominant type, which can mimic relapsing remitting multiple sclerosis (RRMS), the predominant form of classical multiple sclerosis (CMS), on initial presentation [2-8]. Common relapsing NMO patients develop recurrent attacks of longitudinally extensive transverse myelitis (LETM) with MRI signal abnormalities extending over 3 or more spinal cord segments and severe ON resulting in frequent and early attack-related permanent disabilities and even mortality [2-6,8,9]. About 50% of patients require assistance with walking and 62% become functionally blind (visual acuity of 20/200 or worse) within 5 years of onset [2]; and ~15-30% die, predominantly from respiratory failure complicating high cervical myelitis, brainstem involvement and fatal dysautonomia [2-6,8,9]. Lennon and colleagues discovered a biomarker for NMO; NMO-IgG is an autoantibody initially detected in the serum of 73% of NMO but less than 5% of CMS patients [10], which binds to aquaporin-4 (AQP4) [11], the most abundant water Propyzamide channel in the CNS [12-14]. Differences in serological (NMO-IgG seropositivity rates), clinical, neuroradiological and histological characteristics between NMO and CMS have been described, which support the idea that NMO is usually distinct from CMS [2-6,8-10,15-24]. Detection of NMO-IgG or AQP4 autoantibodies is usually clinically useful for early diagnosis of Propyzamide NMO and its related spectrum disorders (NMOSD), including single attack or recurrent LETM without ON, and recurrent ON without ATM; and especially early distinction between NMOSD and CMS [3]. This is critical for proper long-term treatment of patients, as prompt initiation of immunosuppressive medications such as azathioprine with corticosteroid is usually indicated in NMOSD to prevent relapse whereas immunomodulatory therapies such as beta-interferon and natalizumab may be indicated in CMS [3,7,25-28]. NMO-IgG was first identified by indirect immunofluorescence assay (IIFA) using mouse cerebellum as substrate [10]. Subsequently, other semiquantitative and quantitative techniques have been reported for detection of AQP4 autoantibodies in serum and cerebrospinal fluid (CSF) of NMOSD patients including radioimmunoprecipitation [29], fluorescent-based immunoprecipitation assay (FIPA) [30,31], enzyme-linked immunosorbant assay (ELISA) [32], western blot [33] and cell-based IIFA [30,34]. AQP4 autoantibodies seropositivity rates are reported to be higher by IIFA using transfected mammalian cells which express human AQP4 on their cell membranes (cell-based IIFA) than by IIFA using mammalian CNS tissue (tissue-based IIFA). The optimal assay to detect AQP4 autoantibodies Rabbit Polyclonal to MARCH3 for efficient large-scale clinical support has not been ascertained. In this communication, we compared AQP4 autoantibodies seropositivity rates detected by tissue-based IIFA and cell-based IIFA. Patients and Methods Patients Inclusion and exclusion criteria, treatments, Propyzamide follow-up and assessment of patients were as described previously [8] except that in this study, we recruited Hong Kong Chinese patients with CNS IDD of duration 2 years or.
