title: Serum diamine oxidase activity as a diagnostic test for histamine intolerance.
abstract: BACKGROUND
  Histamine intolerance (HIT) is characterized by an imbalance between histamine intake and the capacity for histamine degradation. The main enzyme for metabolizing ingested histamine is diamine oxidase (DAO). Determining DAO activity in serum may be useful in diagnosing HIT.
  
  
  METHODS
  Over a period of 3.5 years we recruited 316 subjects with clinically suspected HIT and 55 healthy controls. Serum DAO activity was measured with a quantitative enzyme immunoassay. Twenty patients with highly reduced DAO activity went on a histamine-free diet for 6-12 months. Afterwards, their DAO activity was determined again.
  
  
  RESULTS
  We found that DAO activity was significantly lower in patients than in healthy control subjects (P < 0.0001). Furthermore, 54 patients had highly reduced serum DAO activity (< 40 HDU/ml). Their main symptoms involved the skin, gastrointestinal tract, respiratory system, and eyes. In all the 20 patients with highly reduced DAO activity, the main clinical symptoms typical of histamine intolerance disappeared after they adopted a histamine-free diet. Furthermore, the serum DAO activity values measured increased significantly (P < 0.0001).
  
  
  CONCLUSIONS
  Our results suggest that determining DAO activity in serum is a useful tool in diagnosing HIT. Furthermore, our results showed the benefit of a histamine-free diet because after the diet the majority of symptoms disappeared and the serum DAO activity significantly increased.
authors.affiliation: University Clinic of Respiratory and Allergic Diseases Golnik, Golnik 36, 4204 Golnik, Slovenia.
authors.forename: Ema
authors.initials: E
authors.lastname: Mušič
authors.forename: Peter
authors.initials: P
authors.lastname: Korošec
authors.forename: Mira
authors.initials: M
authors.lastname: Šilar
authors.forename: Katja
authors.initials: K
authors.lastname: Adamič
authors.forename: Mitja
authors.initials: M
authors.lastname: Košnik
authors.forename: Matija
authors.initials: M
authors.lastname: Rijavec
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006631:Amine Oxidase (Copper-Containing) / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay / Q000706:statistics & numerical data*; D005260:Female; D005512:Food Hypersensitivity / Q000175:diagnosis* / Q000201:enzymology* / Q000453:epidemiology; D006632:Histamine / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D017524:Slovenia / Q000453:epidemiology; D055815:Young Adult
chemical_list: D015415:Biomarkers; D006632:Histamine; D006631:Amine Oxidase (Copper-Containing)