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J Clin Neurol. 2017 Apr;13(2):175-180. doi: 10.3988/jcn.2017.13.2.175. Epub 2017 Mar 6.

Large-Scale in-House Cell-Based Assay for Evaluating the Serostatus in Patients with Neuromyelitis Optica Spectrum Disorder Based on New Diagnostic Criteria.

Kim Y1,2, Kim G1,2, Kong BS1,2, Lee JE2,3, Oh YM2,3, Hyun JW1, Kim SH1, Joung A1, Kim BJ4, Choi K3, Kim HJ1,5.

Author information

1
Department of Neurology, Research Institute and Hospital of National Cancer Center, Goyang, Korea.
2
Division of Translational and Clinical Research II, Research institute, National Cancer Center, Goyang, Korea.
3
Department of Biochemistry and Molecular Biology, and Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea.
4
Department of Neurology, Sungkyunkwan University School of Medicine, Seoul, Korea.
5
Division of Translational and Clinical Research II, Research institute, National Cancer Center, Goyang, Korea. hojinkim@ncc.re.kr.

Abstract

BACKGROUND AND PURPOSE:

The detection of aquaporin 4-IgG (AQP4-IgG) is now a critical diagnostic criterion for neuromyelitis optica spectrum disorder (NMOSD). To evaluate the serostatus of NMOSD patients based on the 2015 new diagnostic criteria using a new in-house cell-based assay (CBA).

METHODS:

We generated a stable cell line using internal ribosome entry site-containing bicistronic vectors, which allow the simultaneous expression of two proteins (AQP4 and green fluorescent protein) separately from the same RNA transcript. We performed in-house CBA using serum from 386 patients: 178 NMOSD patients diagnosed according to the new diagnostic criteria without AQP4-IgG, 63 high risk NMOSD patients presenting 1 of the 6 core clinical characteristics of NMOSD but not fulfilling dissemination in space, and 145 patients with other neurological diseases, including 66 with multiple sclerosis. The serostatus of 111 definite and high risk NMOSD patients were also tested using a commercial CBA kit with identical serum to evaluate the correlation between the 2 methods. All assays were performed by two independent and blinded investigators.

RESULTS:

Our in-house assay yielded a specificity of 100% and sensitivities of 80% (142 of 178) and 76% (48 of 63) when detecting definite- and high risk NMOSD patients, respectively. The comparison with the commercial CBA kit revealed a correlation for 102 of the 111 patients: no correlation was present in 7 patients who were seronegative using the commercial method but seropositive using the in-house method, and in 2 patients who were seropositive using the commercial method but seronegative using the in-house method.

CONCLUSIONS:

These results demonstrate that our in-house CBA is a highly specific and sensitive method for detecting AQP4-IgG in NMOSD patients.

KEYWORDS:

aquaporin 4; aquaporin 4-IgG; cell-based immunofluorescence assay; neuromyelitis optica spectrum disorder

Conflict of interest statement

Kim YS, Kim GY, Kong BS, Lee JE, Oh YM, Hyun JW, Kim SH, Joung AR, Kim BJ and Choi KH report no conflicts of interest. Dr. Kim HJ has lectured, consulted, and received honoraria from Bayer Schering Pharma, Biogen, Genzyme, HanAll BioPharma, MedImmune, Merck Serono, Novartis, Teva-Handok, and UCB; received a grant from the Ministry of Science; and accepted research funding from ICT & Future Planning, Genzyme, Kael-GemVax, Merck Serono, Teva-Handok, and UCB. He serves on a steering committee for MedImmune and as a co-editor for the Multiple Sclerosis Journal-Experimental, Translational, and Clinical. He also serves as an associated editor for the Journal of Clinical Neurology.

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