title: Biopsy location for direct immunofluorescence in patients with suspected bullous pemphigoid impacts probability of a positive test result.
abstract: BACKGROUND
  Bullous pemphigoid (BP) is an autoimmune polymorphic skin disease characterized by erythematous papules and plaques and tense bullae. A skin biopsy for direct immunofluorescence (DIF) is used to detect autoantibodies and complement proteins.
  
  
  OBJECTIVE
  We sought to determine which location would provide the highest probability of obtaining a positive DIF result.
  
  
  METHODS
  We undertook a retrospective chart review of 1,423 DIF biopsies. Biopsies with a clinical suspicion of BP were designated as either lesional, perilesional, or indeterminate.
  
  
  RESULTS
  Fifty percent of lesional DIF biopsies were positive, whereas 22% of perilesional and 12% of indeterminate biopsies had a positive DIF result. The odds ratio of a positive DIF from a lesional versus perilesional biopsy site was found to be 3.45 (95% CI 1.44-8.29).
  
  
  CONCLUSIONS
  Clinicians are more likely to obtain a positive DIF result from a lesional nonbullous skin biopsy than from a perilesional or normal skin biopsy.
authors.forename: Chris
authors.initials: C
authors.lastname: Sladden
authors.forename: Mark G
authors.initials: MG
authors.lastname: Kirchhof
authors.forename: Richard I
authors.initials: RI
authors.lastname: Crawford
mesh_terms: D001323:Autoantibodies / Q000032:analysis*; D001706:Biopsy / Q000379:methods; D019085:Fluorescent Antibody Technique, Direct; D006801:Humans; D010391:Pemphigoid, Bullous / Q000175:diagnosis* / Q000276:immunology*; D011336:Probability; D012189:Retrospective Studies; D012867:Skin / Q000737:chemistry* / Q000473:pathology
chemical_list: D001323:Autoantibodies