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How Airway Caliber Affects FeNO Thresholds Used to Identify Type 2 Inflammation in Asthma
Alain Michils1, Amaryllis Haccuria1, Myrna Virreira1
1Chest Department, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium.
Summary
Airway caliber significantly impacts fractional exhaled nitric oxide (FeNO) levels in asthma, similar to type 2 airway inflammation. Lower lung function (FEV1) requires lower FeNO thresholds to detect active inflammation.
Area of Science:
- Pulmonology
- Biomarkers
- Asthma Research
Background:
- Fractional exhaled nitric oxide (FeNO) is a biomarker for type 2 airway inflammation (T2 AI), reflecting IL-13 activity.
- Reduced airway caliber can lower FeNO levels, indicating an influence of airway obstruction.
Purpose of the Study:
- Compare contributions of airway IL-13 and caliber to FeNO in asthma patients.
- Investigate how reduced airway caliber affects FeNO thresholds for T2 AI detection.
Main Methods:
- FeNO, FEV1, and sputum induction in 120 asthma patients and 13 controls.
- Identified active T2 AI by elevated sputum IL-13, IL-5, or eosinophils.
- Assessed IL-13 and FEV1 contributions to FeNO using multivariable models and ROC analysis.
Main Results:
- Both IL-13 and FEV1 significantly contributed to FeNO in T2 AI patients (P = .005, P = .008).
- FeNO threshold for >85% specificity was 45 ppb overall, dropping to 22 ppb for FEV1 <70%.
Conclusions:
- Airway caliber is a major determinant of FeNO in asthma, as significant as T2 AI.
- Optimal FeNO thresholds for detecting T2 AI decrease with reduced FEV1.
- New FeNO thresholds accounting for lung function are needed in larger studies.
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