title: Serum-positive and -negative AQP4 antibody NMO in Chinese patients.
abstract: OBJECTIVE
  To compare the clinical features of our sero-negative and sero-positive neuromyelitis optica (NMO) patients.
  
  
  METHODS
  Thirty-nine patients with NMO were recruited and analyzed retrospectively. Serum aquaporin 4 (AQP4) antibody status was determined by a cell-based assay. For the sero-negative patients, cerebrospinal fluid (CSF) and serum samples were re-tested using the cell-based assay and an indirect immunofluorescence assay.
  
  
  RESULTS
  By the cell-based assay, 30 patients (76.92%, 30/39), were positive for AQP4 antibodies in serum and 37 patients (94.9%, 37/39), had a CSF-positive antibody status. Seven NMO patients (17.9%, 7/39) were sero-negative by the cell-based assay but demonstrated positive CSF results. By indirect immunofluorescence, the remaining two patients, who had no AQP4 antibodies in serum or CSF by the cell-based assay, were positive for IgG antibodies in serum, which selectively targeted the central nervous system microvessels, pia, subpia, Virchow-Robin space, kidney, and stomach. There were no significant differences between the sero-positive and sero-negative NMO groups among their demographic and clinical data.
  
  
  CONCLUSIONS
  Repeating the test using a different assay or CSF is helpful to clarify whether sero-negative NMO patients do in fact carry AQP4 antibodies.
authors.affiliation: Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong Province, People's Republic of China.
authors.forename: Youming
authors.initials: Y
authors.lastname: Long
authors.forename: Zhengqi
authors.initials: Z
authors.lastname: Lu
authors.forename: Xueqiang
authors.initials: X
authors.lastname: Hu
mesh_terms: D000328:Adult; D051401:Aquaporin 4 / Q000276:immunology*; D044466:Asian People; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D002681:China; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009471:Neuromyelitis Optica / Q000097:blood / Q000276:immunology*
chemical_list: D051401:Aquaporin 4; D001323:Autoantibodies