Serum Level of Indolamine 2, 3-Dioxygenase as a Marker in the Evaluation of Atopic Asthma

BACKGROUND: The changes in amino acid catabolism contribute to the regulation of immune system. The role of indoleamine 2,3-dioxygenase (IDO), and enzyme that mediates the catabolism of tryptophan (trp), remains a controversy. The aim of this study was to determine the relationship between serum level of IDO and the extent of asthma control in patients with allergic bronchial asthma. METHODS:This was a cross-sectional study enrolling 40 atopic patients with allergic bronchial asthma; 20 patients with controlled asthma and 20 patients with uncontrolled asthma. Asthma diagnosis and the level of asthma severity and control were established according to The Global Initiative for Asthma (GINA) recommendations 2012. Atopy was defined by the presence of at least one positive skin prick test reaction to common environmental allergens. Total serum immunoglobulin E (IgE) and serum IDO concentration were measured in all patients. Twenty healthy individuals were included in this study to determine the cutoff level of serum IDO. We used unpaired t-test and Fisher's exact test for determining statistical significance. RESULTS:Serum IDO levels were significantly different across the three study groups (p