title: Opportunistic infections are preceded by a rapid fall in antineutrophil cytoplasmic antibody (ANCA) titer in patients with ANCA associated vasculitis.
abstract: OBJECTIVE
  To study the clinical course and changes in antineutrophil cytoplasmic antibody (ANCA) titers in patients with ANCA associated vasculitis (AAV) who developed opportunistic infections.
  
  
  METHODS
  Among the patients with AAV tested in the Immunopathology Laboratory at the Massachusetts General Hospital between 1989 and 1998, all patients who experienced opportunistic infections (n = 16) were included. We retrospectively studied their clinical features and examined the relationship between changes in ANCA titer and the onset of the opportunistic infections. ANCA titers were measured by antigen-specific ELISA.
  
  
  RESULTS
  Of the 16 AAV patients with opportunistic infection, 15 had no evidence for active vasculitis at the time of the infection. Among these 15 patients, opportunistic infections were associated with a steep fall in ANCA titers. There was no consistent pattern of change in C-reactive protein levels. In 7 patients, the immunosuppressive regimen was increased for new clinical findings shortly before the diagnosis of an opportunistic infection, despite the absence of histologic documentation of active vasculitis. Three of these 7 patients died. One patient, who did not experience a significant fall in ANCA titer. i.e., less than 4-fold from his prior peak, was simultaneously found to have Pneumocystis carinii pneumonia and biopsy proven active vasculitis.
  
  
  CONCLUSIONS
  Our data strongly suggest that opportunistic infections in patients with AAV are associated with negative or rapidly falling ANCA titers. Therefore, changes in ANCA titer can help distinguish opportunistic infections from vasculitis flares when patients with AAV present with indeterminate clinical findings.
authors.affiliation: Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
authors.forename: Runolfur
authors.initials: R
authors.lastname: Palsson
authors.forename: Hyon K
authors.initials: HK
authors.lastname: Choi
authors.forename: John L
authors.initials: JL
authors.lastname: Niles
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood* / Q000276:immunology; D015415:Biomarkers; D005260:Female; D006801:Humans; D007165:Immunosuppression Therapy; D008297:Male; D008875:Middle Aged; D009894:Opportunistic Infections / Q000150:complications / Q000276:immunology*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D014657:Vasculitis / Q000276:immunology* / Q000382:microbiology*
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers