Changes in cd4+cd25+foxp3+ treg cells and inf‐γ between sublingual and subcutaneous immunotherapy with house dust mite in chinese patients with allergic rhinitis

flow limitation. A major site of airflow limitation in COPD is the small conducting airways. Small Airway Obstruction is a harbinger of COPD and abnormalities in the small airways in smokers may or may not have COPD. Thus the aim of the study is early detection of small airway obstruction and determine the Correlation of Forced Expiratory Flow (FEF) 25–75% and the number of pack-years among smokers. Methods: Patient with smoking history is included and demographic and spirometry result (FEV1/FVC, FVC, FEV1, FEF25-75) are collected. Cut-off value of smoking pack-years with low FEF25-75 was determine and correlation among patients with normal and low FEV1/FVC was done. Results: There was significant correlation of FEF 25–75 and smoking pack-years with inverse relationship (r = −0.35, P = 0.0014). The smoking pack-years cut-off value that will give low FEF25-75 was 16.5 smoking pack-years. Conclusion: FEF25-75 may be use for early detection of small airway obstruction. This may help encourage smokers to quit earlier before significant airway obstruction symptomatology occurs and prevent further progression to COPD and other complications of smoking.