Background: Inhaled antigen increases exhaled nitric oxide (eNO) in atopic asthmatics. Recent study showed that the increase of eNO levels was observed in late response (8-10 hours after inhaled antigen) but not in early response (1.5 hour after inhaled antigen). But we recognized that in some asthmatics eNO levels were increased during early response induced by antigen.
Methods: Atopic stable subjects with asthma induced by specific antigen (mite 11, housedust 3) were recruited in this study. Through bronchial provocation test with Mite or Housedust antigen, eNO levels were examined. As the control group, 7 atopic asthmatics who were not induced by specific antigen were recruited.
Results: In 7 subjects, the levels of eNO were increased during early response after inhaled antigen, and in other 7 subjects the levels of eNO were decreased. There were significant difference in the falling of FEV1 at threshold between the two groups (eNO increased group vs eNO decreased group, 22.1+/-0.87 (%) vs. 44.2+/-6.57 (%), p=0.016). In 6 subjects in control group, the levels of eNO were decreased.
Conclusion: Inhaled antigen increased the levels of eNO in some asthmatics during early response in bronchial provocation test. The level of eNO has possibility of predicting the sudden decrease of FEV1 in bronchial provocation test.