title: Clinical features of patients with anti-neutrophil cytoplasmic autoantibodies targeting native myeloperoxidase antigen.
abstract: OBJECTIVE
  Anti-neutrophil cytoplasmic autoantibodies (ANCA) are useful diagnostic markers in systemic vasculitic disorders with small-vessel involvement, but depending on the particular test used, the myeloperoxidase (MPO)-ANCA results are variable. In the present study, we performed a comparative analysis between our originally developed nMPO-ANCA assay that targets the native MPO antigen and other commercially available assays using sera of patients with clinical features of ANCA-associated vasculitis (AAV).
  
  
  METHODS
  Sera of 24 patients strongly suspected of having AAV were examined for the presence of MPO-ANCAs by our nMPO-ANCA assay and by other commercial-based MPO-ANCA assays. These results were correlated to indirect immunofluorescence microscopy staining patterns and patient clinical parameters.
  
  
  RESULTS
  Eighteen out of 24 patients (75 %) were positive for nMPO-ANCA, compared with 13 out of 24 patients (54 %) by one of the most frequently used commercial-based MPO-ANCA enzyme-linked immunosorbent assays (ELISAs) in Japan. Interestingly, the patients who tested positive with our nMPO-ANCA assay alone showed clinical features of AAV marked by continuous fever, polyarthritis, and mild nephritis. The titers of nMPO-ANCA decreased in association with clinical improvement after treatment.
  
  
  CONCLUSIONS
  Our data suggest that a positive nMPO-ANCA result, which identifies antibodies to human native MPO antigen, correlates with AAV disease activity. Moreover, the nMPO-ANCA test has clinical utility in detecting AAV-affected patients who have tested negative using commercially available assays.
authors.affiliation: Department of Rheumatology, Hiroshima Rheumatology Clinic, Hacchobori-Ito-Kyuhodo-Bldg. 3F, 10-13 Teppo-cho, Naka-ku, Hiroshima, 733-0017, Japan, yyamanishi@nifty.com.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamanishi
authors.forename: Toshiko
authors.initials: T
authors.lastname: Ito-Ihara
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Nagao
authors.forename: Kazuko
authors.initials: K
authors.lastname: Uno
authors.forename: Shigeto
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Eri
authors.initials: E
authors.lastname: Muso
authors.forename: Peter Y
authors.initials: PY
authors.lastname: Shane
authors.forename: Gary S
authors.initials: GS
authors.lastname: Firestein
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashimoto
authors.forename: Tomio
authors.initials: T
authors.lastname: Okazaki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Suzuki
mesh_terms: D056648:Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / Q000175:diagnosis* / Q000276:immunology; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005296:Ferrous Compounds; D006801:Humans; D008301:Maleimides; D000075163:Metallocenes; D009195:Peroxidase / Q000276:immunology*; D012680:Sensitivity and Specificity
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D005296:Ferrous Compounds; D008301:Maleimides; D000075163:Metallocenes; C100759:N-(2-ferrocene-ethyl)maleimide; D009195:Peroxidase