title: Aquaporin-4 antibody in neuromyelitis optica: re-testing study in a large population from China.
abstract: BACKGROUND
  Aquaporin-4 (AQP4) antibody sero-positivity is critically important in neuromyelitis optica (NMO). However, the sensitivity of different assays is highly variable. Repeating detection with a highly sensitive assay in a large population is necessary in the case of so-called negative NMO.
  
  
  METHODS
  Retrospective analysis where AQP4 antibodies were detected by commercial cell-based assay (CBA), in-house M23-CBA and in-house M1-CBA.
  
  
  RESULTS
  Of the 1011 serum samples, 206 (20.4%) were sero-positive by primary commercial CBA. In the retest, all 206 participants positive by primary commercial CBA also yielded positive results by in-house M23-CBA and the second commercial CBA again, but only 124 positive in in-house M1-CBA. Among the 805 participants negative by primary commercial CBA, 71 participants were positive for in-house M23-CBA, of which 20 participants were positive for the second commercial CBA, and none were positive by in-house M1-CBA. Of the 171 cerebral spinal fluid samples, 75 (43.9%) were positive by primary commercial CBA. All 75 participants positive by primary commercial CBA also yielded positive results by in-house M23-CBA and the second commercial CBA. Forty-nine (65.3%) of these 75 participants were positive by in-house M1-CBA. Among the 96 participants negative by primary commercial CBA, 15 participants were positive for in-house M23-CBA and none were positive by in-house M1-CBA and the second commercial CBA.
  
  
  CONCLUSIONS
  Different AQP4 isoforms in CBA result in different detection effects, and in-house M23-CBA is the most sensitive method. Some AQP4 antibody-negative NMO may be subject to diagnostic uncertainty due to limitations of the assays.
authors.affiliation: a Department of Neurology , The Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.|b Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and The Ministry of Education of China , Institute of Neuroscience and the Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.
authors.forename: Youming
authors.initials: Y
authors.lastname: Long
authors.affiliation: a Department of Neurology , The Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.|b Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and The Ministry of Education of China , Institute of Neuroscience and the Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.
authors.forename: Junyan
authors.initials: J
authors.lastname: Liang
authors.affiliation: a Department of Neurology , The Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.|b Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and The Ministry of Education of China , Institute of Neuroscience and the Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhong
authors.affiliation: a Department of Neurology , The Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.|b Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and The Ministry of Education of China , Institute of Neuroscience and the Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.
authors.forename: Linzhan
authors.initials: L
authors.lastname: Wu
authors.affiliation: c Department of Neurology , The Third Affiliated Hospital of Sun Yat-Sen University , Guangzhou , China.
authors.forename: Wei
authors.initials: W
authors.lastname: Qiu
authors.affiliation: a Department of Neurology , The Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.|b Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and The Ministry of Education of China , Institute of Neuroscience and the Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.
authors.forename: Shaopeng
authors.initials: S
authors.lastname: Lin
authors.affiliation: a Department of Neurology , The Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.|b Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and The Ministry of Education of China , Institute of Neuroscience and the Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.
authors.forename: Cong
authors.initials: C
authors.lastname: Gao
authors.affiliation: d Department of Emergency , The Second Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Chen
authors.affiliation: e Department of Neurology , The Affiliated Hospital of Qingdao University , Qingdao , China.
authors.forename: Xueping
authors.initials: X
authors.lastname: Zheng
authors.affiliation: f Department of Neurology , The Fifth Affiliated Hospital of GuangZhou Medical University , GuangZhou , China.
authors.forename: Ning
authors.initials: N
authors.lastname: Yang
authors.affiliation: g Department of Neurology , The Second Chinese Medicine Hospital of Guangdong Province , Guangzhou , China.
authors.forename: Min
authors.initials: M
authors.lastname: Gao
authors.affiliation: h Department of Neurology , Guangdong 999 Brain Hospital , Guangzhou , China.
authors.forename: Zhanhang
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D051401:Aquaporin 4 / Q000235:genetics / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood* / Q000134:cerebrospinal fluid; D002681:China / Q000453:epidemiology; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D009471:Neuromyelitis Optica / Q000097:blood* / Q000134:cerebrospinal fluid / Q000175:diagnosis* / Q000276:immunology; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D014162:Transfection; D055815:Young Adult
chemical_list: D051401:Aquaporin 4; D001323:Autoantibodies
keywords: Neuromyelitis optica; aquaporin-4; diagnosis; test