title: Epitope mapping of antibodies against ferritin heavy chain in giant cell arteritis and polymyalgia rheumatica.
abstract: OBJECTIVE
  In a previous study we found an association between antibodies against the human ferritin heavy chain (HFC) protein and giant cell arteritis (GCA) and/or polymyalgia rheumatica (PMR), especially in GCA/PMR patients prior to glucocorticoid treatment. Antibodies against the N-terminal part of ferritin were present in 92% of untreated patients, 69% of patients with disease flare, and 13% of patients in remission. These antibodies appeared to be markers for the early detection of a disease complex usually diagnosed with considerable delay. Our aim in this study was to optimize the diagnostic test by epitope mapping of antibodies against HFC using peptide antigens in enzyme-linked immunosorbent assays (ELISAs).
  
  
  METHODS
  We evaluated serum samples from a selected group of GCA/PMR patients in whom the sensitivity of antibodies against the N-terminal ferritin peptide was only 35%. Patients with late-onset rheumatoid arthritis (LORA), patients with fever, patients with granulomatosis with polyangiitis (GPA), patients without any autoimmune disease at age > 65 years, and blood donors served as controls.
  
  
  RESULTS
  By combining different ELISAs we were able to increase the frequency of human ferritin peptide antibodies in GCA/PMR (p < 0.0001) without significantly altering the false-positive rate (FPR) of the diagnostic test. The frequency of antibodies against human ferritin peptide increased from 53% to 74% in GCA/PMR patients with disease flare, from 29% to 40% in GCA/PMR patients in partial remission, and from 8% to 45% in GCA/PMR patients in complete remission.
  
  
  CONCLUSIONS
  The potential diagnostic test for GCA/PMR can be improved by combining three human ferritin peptide antibodies.
authors.affiliation: Department of Immunology and Rheumatology, Medical University Hannover, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Große
authors.forename: R E
authors.initials: RE
authors.lastname: Schmidt
authors.forename: T
authors.initials: T
authors.lastname: Witte
authors.forename: N T
authors.initials: NT
authors.lastname: Baerlecken
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001052:Apoferritins / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D018604:Epitope Mapping; D005260:Female; D013700:Giant Cell Arteritis / Q000097:blood / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011111:Polymyalgia Rheumatica / Q000097:blood / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D001052:Apoferritins