Features of anti-aquaporin 4 antibody-seronegative Thai patients with neuromyelitis optica spectrum disorders: a comparison with seropositive cases.

ABSTRACT

OBJECTIVE: The aim of this study is to investigate the unique features of seronegative neuromyelitis optica spectrum disorders (NMOSD) in Thailand. BACKGROUND: It remains unknown whether seronegative NMOSD patients possess clinical and paraclinical features that are distinct from those with seropositivity. METHODS: In a Thai cohort of idiopathic inflammatory CNS disorders (n=122), 52 patients fulfilled the Wingerchuk 2007 criteria for NMOSD. We determined anti-AQP4 antibody statuses using three different assays (an in-house cell-based assay [CBA], a commercially available CBA and a tissue-based indirect immunofluorescence [IIF] assay). RESULTS: Among the NMOSD patients, the percentage of seropositive cases was 54.5% based on the in-house and commercial CBAs and 30.8% based on the IIF assay. Using the in-house CBA, seronegative NMOSD patients exhibited distinct features compared with seropositive patients, such as a lack of female preponderance (F/M=1.2 vs. 6.0), frequent simultaneous bilateral optic involvement (33.3% vs. 0.04%), a lower annual relapse rate (0.4 ± 0.3 vs. 0.7 ± 0.6), fewer spinal cord lesions (1.0 ± 4.3 vs. 1.4 ± 0.6), and lower CSF cell counts (20 ± 72 vs. 80 ± 285). Use of the commercial CBA yielded essentially similar results, but some of these differences were not significant using IIF. CONCLUSIONS: Sensitive anti-AQP4 antibody assays reveal features of seronegative NMOSD patients that differ from those of seropositive patients from Thailand.