ABSTRACT
BACKGROUND: Well-known allergy tests are used to evaluate and diagnose allergic diseases. The aim of this study was to assess the role of serum level diamine oxidase (DAO) enzyme as a diagnostic marker in respiratory allergy. METHODS: This case-control study included 40 patients with respiratory allergies (atopic asthma and allergic rhinitis) as well as 40 age- and sex-matched controls. A detailed past medical history of allergy was collected from each participant including family history of allergy. Physical examination, pulmonary function test (PFT) and measurement of serum levels of total immunoglobulin E (IgE) and DAO were performed. Skin-prick test and specific IgE to common aeroallergens were also carried out. RESULTS: DAO levels were higher in patients than controls. There was a positive correlation between severity of disease and DAO. No significant association was found between DAO level and age, type of respiratory allergy, duration of disease, PFT, eosinophilia, and total IgE. DAO had a high negative predictive value (94.7%) and high sensitivity (97.5%). CONCLUSION: DAO may be helpful in the assessment of severity and in ruling out respiratory allergy.