title: Comparison of diagnostic accuracy of microscopy and flow cytometry in evaluating N-methyl-D-aspartate receptor antibodies in serum using a live cell-based assay.
abstract: N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune neurological disease, diagnosed by a specific autoantibody against NMDAR. Antibody testing using commercially available cell-based assays (CBA) or immunohistochemistry on rat brain tissue has proven high specificity and sensitivity. Here we compare an immunofluorescence live CBA to a flow cytometry (FACS) based assay to detect NMDAR antibodies by their binding to the surface of HEK293A cells functionally expressing NMDAR. Both assays were first established using a discovery group of 76 individuals and then validated in a group of 32 patients in a blinded manner. In the CBA, 23 of 23 patients with NMDAR encephalitis were positive for NMDAR antibodies and 0 of 85 controls (32 healthy controls and 53 patients with other neurological diseases), resulting in a sensitivity and specificity of 100% (95% confidence intervals (CI) 85.1-100.0 and 95.7-100.0, respectively). The FACS based assay detected NMDAR antibodies in 20 of 23 patients and in 0 of 85 controls. Therefore, with an equally high specificity (95% CI 95.7-100.0) the sensitivity of the FACS based assay was 87% (95% CI 66.4-97.2). Comparing antibody titers from CBA with delta median fluorescence intensities from FACS showed a high concordance (kappa = 0.943, p<0.0001) and correlation (r = 0.697, p<0.0001). In conclusion, evaluation of the FACS based assay revealed a lower sensitivity and high inter-assay variation, making the CBA a more reliable detection method.
authors: Clinical Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors: Melanie
authors: M
authors: Ramberger
authors: Clinical Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors: Patrick
authors: P
authors: Peschl
authors: Clinical Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors: Kathrin
authors: K
authors: Schanda
authors: Division of Neuroanatomy, Medical University of Innsbruck, Innsbruck, Austria.
authors: Regina
authors: R
authors: Irschick
authors: Institute of Neurology, Medical University of Vienna, Vienna, Austria; Institució Catalana de Recerca i Estudis Avançats (ICREA), IDIBAPS, Hospital Clínic, Barcelona, Spain.
authors: Romana
authors: R
authors: Höftberger
authors: Clinical Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors: Florian
authors: F
authors: Deisenhammer
authors: Pediatric Neurology, Witten/Herdecke University, Children's Hospital Datteln, Datteln, Germany.
authors: Kevin
authors: K
authors: Rostásy
authors: Clinical Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors: Thomas
authors: T
authors: Berger
authors: Institució Catalana de Recerca i Estudis Avançats (ICREA), IDIBAPS, Hospital Clínic, Barcelona, Spain.
authors: Josep
authors: J
authors: Dalmau
authors: Clinical Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors: Markus
authors: M
authors: Reindl
mesh_terms: D000293:Adolescent; D000328:Adult; D060426:Anti-N-Methyl-D-Aspartate Receptor Encephalitis / Q000097:blood*; D001323:Autoantibodies / Q000097:blood*; D016022:Case-Control Studies; D002648:Child; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008856:Microscopy, Fluorescence / Q000379:methods; D016194:Receptors, N-Methyl-D-Aspartate / Q000276:immunology; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000379:methods*
chemical_list: D001323:Autoantibodies; D016194:Receptors, N-Methyl-D-Aspartate