title: Plasma poltergeists: a negative cortisol interference leading to a false diagnosis of adrenal insufficiency.
abstract: BACKGROUND
  Adrenal insufficiency is a rare life threatening condition with non-specific clinical signs and symptoms. This necessitates a high level of reliance on laboratory results for making the diagnosis.
  
  
  METHODS
  We report a case involving an interference in cortisol measurement leading to spuriously low-cortisol measurements and the incorrect diagnosis and treatment of adrenal insufficiency. We also discuss the testing used to confirm the presence and nature of the interferent.
  
  
  RESULTS
  Interference with an IgG antibody was demonstrated, and the patient was found to have a normally functioning adrenal axis.
  
  
  CONCLUSIONS
  Interference in immunoassay is well described but often difficult to detect in clinical practice. Negative interference in cortisol measurement can occur and may lead to inappropriate diagnosis and treatment.
authors.affiliation: Department of Biochemistry, Wellington Hospital, Capital and Coast District Health Board, Wellington, New Zealand. Damon.Bell@health.wa.gov.au
authors.forename: Damon A
authors.initials: DA
authors.lastname: Bell
authors.forename: Chris M
authors.initials: CM
authors.lastname: Florkowski
authors.forename: John G
authors.initials: JG
authors.lastname: Lewis
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Crooke
mesh_terms: D000309:Adrenal Insufficiency / Q000097:blood / Q000175:diagnosis*; D003951:Diagnostic Errors; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood* / Q000627:therapeutic use; D007074:Immunoglobulin G; D008875:Middle Aged; D017211:Treatment Failure
chemical_list: D007074:Immunoglobulin G; D006854:Hydrocortisone