title: Antiacquaporin 4 antibodies detection by different techniques in neuromyelitis optica patients.
abstract: BACKGROUND
  Antibodies against aquaporin-4 (AQP4), a water channel particularly expressed on perivascular astrocytic podocytes, are proposed as a marker for the diagnosis of neuromyelitis optica (NMO). However, a consensus on seroprevalence and optimal detection method has not yet been reached.
  
  
  OBJECTIVE
  To investigate the performance of different assays to detect anti-AQP4 antibodies.
  
  
  METHODS
  We set up five different assays. Two of them were capable to detect perivascular IgG reactivity on brain tissue by immunofluorescence (NMO-IgG). Other three assays have been set to detect anti-AQP4 antibodies: immunofluorescence and flow cytometry on AQP4-expressing cells, and a radioimmunoprecipitation assay. We assessed sensitivity and specificity of these assays by interrogating sera of 33 NMO patients, 13 patients at high risk to develop NMO (hrNMO), 6 patients affected by acute partial transverse myelitis (APTM), 20 patients with multiple sclerosis (MS), and 67 age- and sex-matched healthy controls.
  
  
  RESULTS
  We found that the presence of serum NMO-IgG and anti-AQP4 reactivity is almost exclusively restricted to patients with NMO and hrNMO. Seroprevalence and sensitivity ranged from 30 to 47%, depending on the assay. Specificity ranged from 95 to 100%. Comparing results obtained in the five assays, we noticed lack of concordance in some samples.
  
  
  CONCLUSIONS
  Detection of NMO-IgG or anti-AQP4 antibodies may represent a valuable tool to assist neurologists in the differential diagnosis between patients with NMO, hrNMO, APTM, or MS. The current lack of a gold standard to detect anti-AQP4 antibodies implies the necessity to standardize the detection of these antibodies.
authors: Institute of Experimental Neurology (INSpe), Department of Neurology, San Raffaele Scientific Institute, Milan, Italy.
authors: R
authors: R
authors: Fazio
authors: M L
authors: ML
authors: Malosio
authors: V
authors: V
authors: Lampasona
authors: D
authors: D
authors: De Feo
authors: D
authors: D
authors: Privitera
authors: F
authors: F
authors: Marnetto
authors: D
authors: D
authors: Centonze
authors: A
authors: A
authors: Ghezzi
authors: G
authors: G
authors: Comi
authors: R
authors: R
authors: Furlan
authors: G
authors: G
authors: Martino
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000918:Antibody Specificity; D051401:Aquaporin 4 / Q000276:immunology*; D001323:Autoantibodies / Q000032:analysis / Q000097:blood*; D001921:Brain / Q000276:immunology; D002648:Child; D015331:Cohort Studies; D003937:Diagnosis, Differential; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis / Q000276:immunology; D009188:Myelitis, Transverse / Q000175:diagnosis / Q000276:immunology; D009471:Neuromyelitis Optica / Q000097:blood* / Q000175:diagnosis / Q000209:etiology / Q000276:immunology*; D015531:Radioimmunoprecipitation Assay; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016036:Seroepidemiologic Studies; D055815:Young Adult
chemical_list: C496030:AQP4 protein, human; D051401:Aquaporin 4; D001323:Autoantibodies; D007074:Immunoglobulin G