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Updated: Jul 26, 2025
Methodology for Sputum Induction and Laboratory Processing
Published on: December 17, 2017
A comparative study on the value of lower airway exhaled nitric oxide combined with small airway parameters for
Haodong Bai1, Cuiqin Shi1, Sue Yu1
1Department of Pulmonary and Critical Care Medicine, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China.
Background:
The diagnosis of cough-variant asthma (CVA) is based on bronchial provocation test, which is challenging to be conducted. Most CVA patients have type 2 airway inflammation and small airway dysfunction. FeNO200, reflecting small airway inflammation, may be used to diagnose CVA.
Objective:
This study aimed to explore and compare the value of lower airway exhaled nitric oxide (FeNO50, FeNO200, and CaNO) combined with small airway parameters for diagnosing CVA.
Methods:
Chronic cough patients who attended the clinic from September 2021 to August 2022 were enrolled and divided into CVA group (n = 71) and non-CVA (NCVA) group (n = 212). The diagnostic values of FeNO50, FeNO200, concentration of alveolar nitric oxide (CaNO), maximal mid-expiratory flow (MMEF), forced expiratory flow at 75% of forced vital capacity (FEF75%) and forced expiratory flow at 50% of forced vital capacity (FEF50%) for CVA were evaluated.
Results:
FeNO50 [39(39) ppb versus 17(12) parts per billion (ppb), p < 0.01], FeNO200 [17(14) ppb versus 8(5) ppb, p < 0.01] and CaNO [5.0(6.1) ppb versus 3.5(3.6) ppb, p < 0.01] in CVA group were significantly higher than those in NCVA group. The optimal cut-off values of FeNO50, FeNO200, and CaNO for diagnosis of CVA were 27.00 ppb [area under the curve (AUC) 0.88, sensitivity 78.87%, specificity 79.25%], 11.00 ppb (AUC 0.92, sensitivity 88.73%, specificity 81.60%) and 3.60 ppb (AUC 0.66, sensitivity 73.24%, specificity 52.36%), respectively. For diagnosing CVA, the value of FeNO200 was better than FeNO50 (p = 0.04). The optimal cut-off values of MMEF, FEF75%, and FEF50% for the diagnosis of CVA were 63.80% (AUC 0.75, sensitivity 53.52%, specificity 86.32%), 77.9% (AUC 0.74, sensitivity 57.75%, specificity 83.49%) and 73.50% (AUC 0.75, sensitivity 60.56%, specificity 80.19%), respectively. The AUCs of FeNO50 combined with MMEF, FEF75%, and FEF50% for the diagnosis of CVA were all 0.89. The AUCs of FeNO200 combined with MMEF, FEF75%, and FEF50% for the diagnosis of CVA were all 0.93.
Conclusion:
FeNO200 > 11 ppb contributed strongly for differentiating CVA from chronic cough, especially in patients with small airway dysfunction.
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