The Study Of FEV₃/FVC In Detecting Early Airway Obstruction

Objective:To study the significance of FEV3/FVC for detecting early airway obstruction or small airway disease, and add a new more sensitive index for clinical diagnosis.Methods:370 cases of pulmonary function test results were involved in this statistical analysis.The pulmonary function test was inspected in Lanzhou university second hospital from Nov.2014 to Jan.2015. The results were divided into three groups:(A) normal FEV1/FVC and FEV3/FVC:(B)only a reduced FEV3/FVC; (C)reduced FEV1/FVC.Compare the differences of the lung function indexes for the three group.Spearman correlation determined the relationships between FEV3/FVC and small airway indexex.And calculate the sensitivity, specificity, positive predictive value and negative predictive value of FEV3/FVC for judging the airway obstruction.Results:Compared with group A, group B had higher% predicted TLC, residual volume (RV), and RV/TLC %, and lower% predicted FEV1, inspiratory capacity(IC) and diffusing capacity of lung for carbon monoxide (DLCO), P<0.05. Compared with group C. group B had lower% predicted TLC, RV, and RV/TLC %, and higher% predicted FEV1, IC and D1CO, P <0.05.FEV3/FVC was correlated positively with MMEF (r=0.602,P<0.001), MEF50(r =0.567, P<0.001) and MEF25 (r=0.637,P<0.001). The sensitivity, specificity, positive predictive value and negative predictive value of FEV3/FVC for judging the airway obstruction is 94.4%,61.7%,37.4%,97.9% respectively.Conclusions:The reduction of FEV3/FVC may indicate an early airway obstruction and small airway disease. The FEV3/FVC should be routinely reported with FEV1/FVC in lung function test.