Predictive Value of the Serum Diamine Oxidase Level in the Diagnosis of Seasonal Allergic Rhinitis.

Background: Allergic rhinitis (AR) is characterized by the increased sensitivity of the nasal mucosa to allergens and has a significant impact on life quality. There is promising evidence that biomarkers can help in the diagnosis, treatment, and follow-up of patients with AR. Diamine oxidase (DAO) is one of the enzymes responsible for the breakdown of histamine, the primary mediator of allergies.

Objective: To investigate the significance of DAO as a useful biomarker for diagnosis and the severity of AR.

Methods: In this case-control study, 24 patients and 24 healthy controls were recruited and their serum DAO levels, total IgE levels (using ELISA), blood eosinophil count, and percentage (using complete blood cell count) were measured. The sino-nasal outcomes test-22 (SNOT-22) questionnaire was used to assess the severity of symptoms in patients. The Receiver Operating Characteristic (ROC) analysis was used to assess the predictive power of DAO level for the diagnosis of AR. The relationship between DAO and disease severity, as well as other AR-related clinical factors, were also investigated.

Results: DAO levels were lower in AR patients compared with the controls. The DAO level did not significantly correlate with the severity of AR according to the Allergic Rhinitis and its Impact on Asthma (ARIA) score, though it was lower in patients with persistent or moderate to severe symptoms. The total IgE, eosinophil percentage, and SNOT-22 score all had an inverse relationship with DAO. Moreover, DAO was significantly associated with the diagnosis of AR, with an Area under the ROC Curve (AUC) of 0.771, a sensitivity of 75%, and a specificity of 62.5%.

Conclusion: DAO might be a valuable biomarker in the diagnosis of allergic rhinitis.