title: Utility of immunofluorescence testing for vascular IgA in adult patients with leukocytoclastic vasculitis.
abstract: OBJECTIVE
  The purpose of this study was to examine the utility of immunofluorescence (IF) testing in patients with leukocytoclastic vasculitis (LCV), particularly with regard to usefulness in the diagnosis of Henoch-Schönlein purpura (HSP).
  
  
  METHODS
  We retrospectively analyzed the results of IF testing in 96 patients with LCV and compared results with clinical criteria and clinical impression at the time of biopsy by review of the medical record.
  
  
  RESULTS
  Sensitivity and specificity of vascular immunoglobulin A (IgA) for the diagnosis of HSP were 0.86 and 0.84, respectively. Positive predictive value was 0.48 and negative predictive value was 0.97. Of the 53 patients with LCV who did not meet clinical criteria for HSP and carried a low clinical suspicion for the disease at the time of biopsy, seven had moderate to strong staining for vascular IgA. Only one of these patients was determined to have HSP.
  
  
  CONCLUSIONS
  Our data confirm that vascular IgA is nonspecific and also demonstrate that the utility of IF studies for vasculitis is influenced by the clinical presentation and the clinician's level of suspicion for HSP. Our data show that the clinical features and the overall clinical impression are helpful in selecting which patients are most likely to benefit from IF testing.
authors.affiliation: From the Department of Pathology, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA.
authors.forename: Allison R
authors.initials: AR
authors.lastname: Larson
authors.affiliation: From the Department of Pathology, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA. sgranter@partners.org.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Granter
mesh_terms: D003937:Diagnosis, Differential; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D011695:IgA Vasculitis / Q000175:diagnosis* / Q000276:immunology; D007070:Immunoglobulin A / Q000032:analysis*; D008297:Male; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018366:Vasculitis, Leukocytoclastic, Cutaneous / Q000175:diagnosis* / Q000276:immunology
chemical_list: D007070:Immunoglobulin A
keywords: Henoch-Schönlein purpura; IgA; Immunofluorescence; Leukocytoclastic vasculitis; Vasculitis