title: IgA antibodies to myeloperoxidase in patients with eosinophilic granulomatosis with polyangiitis (Churg-Strauss).
abstract: OBJECTIVE
  To determine the prevalence of anti-myeloperoxidase (MPO) antibodies of IgA (IgA anti-MPO) isotype in patients with eosinophilic granulomatosis with polyangiitis (EGPA), and the association of the IgA antibodies with IgG anti-MPO and with disease activity.
  
  
  METHODS
  Serum samples from patients with EGPA followed in a multicenter longitudinal cohort were tested by ELISA for the presence of IgA anti-MPO and IgG anti-MPO antibodies. Sera from 87 healthy controls were used to define a positive test. Sera from 168 patients with EGPA (298 samples) were tested. Frequencies of positive testing for IgA anti-MPO were compared between patients with active EGPA, patients in remission, and controls.
  
  
  RESULTS
  IgA anti-MPO was detected in 10 of 168 (6%) patients with EGPA (11 of 298 serum samples) compared to 1 of 87 (1%) healthy controls (p=0.10). All 11 samples testing positive for IgA anti-MPO also tested positive for IgG anti-MPO. Ninety samples tested positive for IgG anti-MPO but negative for IgA. Samples taken during active EGPA were positive for IgA anti-MPO in 6/72 cases (8%), compared to 5/226 (2%) during remission (p=0.03). Among samples taken during moderate or high disease activity, 5/41 were positive (12%, p=0.01 compared to remission).
  
  
  CONCLUSIONS
  Although IgA anti-MPO antibodies are detectable in some patients with EGPA and may be detectable more frequently during active disease, their presence seems unlikely to provide information beyond what is obtained from conventional IgG anti-MPO.
authors.affiliation: Section of Rheumatology, Boston University School of Medicine, Boston, MA; and Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Emory University School of Medicine, Atlanta, GA, USA.
authors.forename: Esha
authors.initials: E
authors.lastname: Oommen
authors.affiliation: Division of Pulmonology, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: Amber
authors.initials: A
authors.lastname: Hummel
authors.affiliation: Helmholtz Zentrum Muenchen, Munich, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Allmannsberger
authors.affiliation: Department of Biostatistics, University of South Florida, FL, USA.
authors.forename: David
authors.initials: D
authors.lastname: Cuthbertson
authors.affiliation: Division of Rheumatology, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Simon
authors.initials: S
authors.lastname: Carette
authors.affiliation: Division of Rheumatology, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Christian
authors.initials: C
authors.lastname: Pagnoux
authors.affiliation: Center for Vasculitis Care and Research, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Gary S
authors.initials: GS
authors.lastname: Hoffman
authors.affiliation: Helmholtz Zentrum Muenchen, Munich, Germany.
authors.forename: Dieter E
authors.initials: DE
authors.lastname: Jenne
authors.affiliation: Division of Rheumatology, St. Joseph's Healthcare, McMaster University, Hamilton, ON, Canada.
authors.forename: Nader A
authors.initials: NA
authors.lastname: Khalidi
authors.affiliation: Division of Rheumatology, University of Utah, Salt Lake City, UT, USA.
authors.forename: Curry L
authors.initials: CL
authors.lastname: Koening
authors.affiliation: Center for Vasculitis Care and Research, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Langford
authors.affiliation: Division of Rheumatology and Clinical Immunology, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Carol A
authors.initials: CA
authors.lastname: McAlear
authors.affiliation: Division of Rheumatology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Larry
authors.initials: L
authors.lastname: Moreland
authors.affiliation: Division of Rheumatology, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Seo
authors.affiliation: Division of Rheumatology and Clinical Immunology, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Antoine
authors.initials: A
authors.lastname: Sreih
authors.affiliation: Division of Rheumatology, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Ytterberg
authors.affiliation: Division of Rheumatology and Clinical Immunology, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Merkel
authors.affiliation: Division of Pulmonology, Mayo Clinic College of Medicine, Rochester, MN, USA.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Specks
authors.affiliation: Section of Rheumatology, Boston University School of Medicine; and Rheumatology Section, VA Boston Healthcare System, Boston, MA, USA. pmonach@bu.edu.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Monach
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D002170:Canada; D016022:Case-Control Studies; D015267:Churg-Strauss Syndrome / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood*; D007074:Immunoglobulin G / Q000097:blood*; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009195:Peroxidase / Q000276:immunology*; D011237:Predictive Value of Tests; D012074:Remission Induction; D016896:Treatment Outcome; D014481:United States; D055815:Young Adult
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D009195:Peroxidase