Abstract
Cough variant asthma (CVA), a common asthma phenotype characterized by nonproductive cough and bronchial hyperreactivity (BHR), is usually detected by bronchial provocation tests (BPTs) which are time-consuming, expensive, and unsafe. The primary study objective was to provide proof of concept for the use of fractional exhaled nitric oxide (FENO), eosinophil count percentage in induced sputum (sEOS%), forced expiratory flow between 25 and 75% of forced vital capacity (FEF25–75%) % predicted value, and FEF25–75% z-scores as surrogate markers predicting BHR in young adults with suspected CVA; the secondary objective was to compare the diagnostic performance of the various techniques. Three hundred and ten subjects (median age 24 years) were included in a cross-sectional study. Subjects were characterized as BHR positive (POS) (n = 147) or BHR negative (NEG) (n = 163) according to methacholine BPT. Classification accuracies were expressed as areas under the receiver operator characteristic curves (AUC). Compared with BHR NEG, FEF25–75% % predicted value and FEF25–75% z-scores were lower in the BHR POS group (p < 0.001), whereas FENO (p < 0.001) and sEOS% were higher (p < 0.001). AUC values for detecting BHR were as follows: FENO, 0.98 (SD = 0.02); sEOS%, 0.98 (SD = 0.02); FEF25–75% % pred, 0.93 (SD = 0.05); FEF25–75% z scores, 0.92 (SD = 0.05). Optimal cutoff values (OCV) for BHR prediction were as follows: FENO, 32.7 ppb (sensitivity = 0.93, specificity = 0.96), sEOS%, 3.80% (sensitivity = 0.94, specificity = 0.94), FEF25–75% % predicted value, 80.0% (sensitivity = 0.90, specificity = 0.87), and FEF25–75% z-score, −0.87 (sensitivity = 0.89, specificity = 0.87). Non-invasive/semi-invasive airway inflammatory or small airway functional measures might be used as surrogate markers predicting BHR in young adults with suspected CVA.
Highlights
Asthma is characterized by chronic airway inflammation, bronchial hyperreactivity (BHR), and episodes of bronchoconstriction clinically presenting as variable and recurring cough, dyspnea, and wheezing
In an opportunistic sample of 310 young adults with Cough variant asthma (CVA), we aimed to provide a proof of concept for the use of fractional exhaled nitric oxide (FENO), sEOS%, FEF25–75% predicted value, and FEF25–75% z scores as surrogate markers predicting BHR
Subjects with positive bronchial provocation tests (BPTs) were categorized as BHR POS (n 147); if BPT was negative, subjects were identified as BHR NEG (n 163)
Summary
Asthma is characterized by chronic airway inflammation, bronchial hyperreactivity (BHR), and episodes of bronchoconstriction clinically presenting as variable and recurring cough, dyspnea, and wheezing (ginasthma, 2020). Asthma is a heterogeneous disease, including a broad spectrum of diseases described as various phenotypes (Haldar et al, 2008). Cough variant asthma (CVA), a frequent asthma phenotype, is characterized by a cough as a prevalent symptom and BHR (Corrao et al, 1979). The presence of BHR is generally detected with bronchial provocation tests (BPTs), a positive response to bronchodilators or both (Irwin et al, 2006; Achilleos, 2016). Safer, and more rapid predictive methods would be relevant to clinical practice (Bao et al, 2018) as they would facilitate the identification of those patients with suspected CVA who need to be referred for BHT
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