Is It Necessary To Perform The Bronchial Dilation Test When The Patient's FEV₁ Is Normal And The Small Airway Function Is Impaired

Objective:The objective of our study was to explore it is necessary to proceed the bronchial dilation test?BDT?when small airway function is impaired but FEV₁ is normal.Also,we try to find the optimal cut-off values of the indicators for small airway function in spirometry that suggest BDT positive.Methods:A total of 499 adult patients?mean age:50.31±13.63?with asthma-related symptoms such as cough,wheezing and chest tightness were collected from Respiratory Medicine Clinic of the First Affiliated Hospital of China Medical University from January 2013 to February 2018.Their baseline spirometry showed normal FEV₁?FVC and FEV₁/FVC but with small airway dysfunction,and had performed BDT.193 were males and 306 were females.Increase in FVC and/or FEV₁ of?12%and?200 ml and/or increase in FEF_50%of?25%and/or increase in FEF_25-75%of?25%from baseline 20 minutes after administration of bronchodilator?salbutamol sulfate?,then we thought that the patient's BDT was positive.Record the relevant data and analyze.Results:Patients with asthma-related symptoms such as cough,wheezing and chest tightness and normal FEV₁?FVC and FEV₁/FVC had lower FEF_50%,FEF_75%,and FEF_25-75%values in BDT positive group compared to negative group.The AUCs of FEF_50%,FEF_75%,and FEF_25-75%for predicting BDT positive were 0.6101?95%CI,0.561,0.659??0.6049?95%CI,0.555,0.655?and 0.6175?95%CI,0.568,0.667?,respectively.Optimal cutoff values for FEF_50%,FEF_75%,and FEF_25-75%were 67.95%?59.75%and 69.25%,respectively.The AUC of FEF50%combined with FEF_25-75%was0.6267?95%CI,0.578,0.675?.The AUC of FEF_50%combined with FEF_75%was 0.6329?95%CI,0.584,0.681?.The AUC of FEF_75%combined with FEF_25-75%was 0.6224?95%CI,0.573,0.671?.The result showed that all the AUCs of the combination measurements were higher compared to the AUCs of either measurement alone.But this didn't have statistical significance.The sample size of our study was not large enough may play a role in it.After tranfering the continuous test variables to dichotomous state variables by using their cut-off values,the AUCs of FEF_50%?FEF_25-75%and FEF_50%combined with FEF_25-75%were 0.5957?95%CI,0.546,0.646??0.5878?95%CI,0.538,0.638?and 0.6156?95%CI,0.566,0.665?,respectively.The P value for the AUCs comparison of FEF_50%?FEF_25-75%with their combination were closed to0.05?P=0.072,P=0.101?.That may indicate if the sample size is large enough,when FEF_50%?67.95%and FEF_25-75%?69.25%,the likelyhood of BDT positive may increase.Also,we found that lower FEF_50%and FEF_75%were the risk factors of BDT positive in patients with asthma-related symptoms such as cough,wheezing and chest tightness and normal FEV₁?FVC and FEV₁/FVC by using the binary logical regression.Conclusion:We found that FEF_50%,FEF_75%,and FEF_25-75%were predictive parameters of BDT positive in patients with asthma-related symptoms such as cough,chest tightness,wheezing,and normal FEV₁?FVC and FEV₁/FVC.The lower the value,the greater the probability of BDT positive.There wasnot statistical significant in the predictive value of this three parameter alone compared to their combination with each other.When FEF_50%?67.95%or FEF_75%?59.75%or FEF_25-75%?69.25%,it could predict BDT positive to a certain extent.