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Bronchial asthma with normal forced expiratory volume in 1 second (FEV1) compared with low FEV1
Akihiko Ohwada1,2, Hiroko Kitaoka3
1Ohwada Clinic, Ichikawa, Japan.
Journal of Thoracic Disease
|October 24, 2024
Summary
Cough variant asthma (CVA) is uncommon in patients with normal lung function (FEV1 ≥90%). Asthmatic patients with normal FEV1 respond well to treatment, indicating mild asthma, but show distinct marker profiles compared to those with reduced FEV1.
Area of Science:
- Pulmonology
- Respiratory Medicine
- Clinical Immunology
Background:
- Cough variant asthma (CVA) presents with cough as the sole symptom and normal pulmonary function, specifically forced expiratory volume in 1 second (FEV1).
- The prevalence of CVA among asthma patients with normal FEV1 remains unclear.
- This study aimed to determine the incidence of cough-only symptoms in patients with normal FEV1 and compare them to typical asthma patients.
Purpose of the Study:
- To evaluate the incidence of cough as the sole symptom in asthma patients with normal FEV1 (≥90% predicted).
- To compare clinical characteristics and treatment responses between asthma patients with normal FEV1 and those with low FEV1 (<90% predicted).
- To investigate the relationship between symptom improvement and biomarkers like FeNO, eosinophils, and IgE in different FEV1 groups.
Main Methods:
- 329 treatment-naive asthma patients were divided into normal FEV1 (≥90%) and low FEV1 (<90%) groups.
- Assessed Visual Analogue Scale (VAS) for cough and dyspnea, FEV1, and fractional exhaled nitric oxide (FeNO) responsiveness to inhaled corticosteroid/long-acting beta2 agonist (ICS/LABA) treatment.
- Correlated changes in symptoms with FEV1, FeNO, peripheral eosinophil count, and serum IgE.
Main Results:
- Only 8.6% of the normal FEV1 group had cough without dyspnea, suggesting few CVA candidates.
- Both groups showed symptom improvement with ICS/LABA, but dyspnea VAS scores remained higher in the low FEV1 group.
- Normal FEV1 patients had lower pre-treatment eosinophils, IgE, and FeNO, and less FEV1 improvement post-treatment compared to the low FEV1 group.
Conclusions:
- Asthma patients with normal FEV1, including potential CVA cases, represent a mild asthma phenotype.
- These patients respond well to ICS/LABA treatment, with symptom improvement correlating with FEV1 changes.
- While overall symptoms were similar, the relationship between symptom improvement and Th2 markers differed between normal and low FEV1 groups.
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