Extended nitric oxide analysis in patients with suspected airway hyperreactivity

OBJECTIVES: a key feature of asthma is airway hyperresponsiveness (AHR), which is typically diagnosed through methacholine challenge testing (MCT). Fractional exhaled nitric oxide (FENO) is a non-invasive marker of type-2 inflammation. Extended nitric oxide analysis breaks this down into bronchial (JawNO) and alveolar (CANO) components; we aimed to determine whether this extensive analysis offers added value in diagnosing AHR beyond what conventional FENO testing can provide. METHODS: seventy-two consecutive patients referred for MCT were prospectively enrolled and underwent spirometry, extended nitric oxide analysis, and MCT. AHR was defined using three methacholine dose thresholds for PD20FEV1 (≤400, ≤800, and ≤1600 µg). RESULTS: AHR prevalence ranged from 23.6% at the lowest threshold (≤400 µg) to 44.4% at the highest (≤1600 µg). Patients with positive AHR had significantly elevated FENO and JawNO across all thresholds. The best FENO and JawNO cut-offs provided strong negative predictive values, but their positive predictive values were low. CONCLUSION: extended nitric oxide analysis - especially FENO and JawNO - may improves the diagnostic capability of exhaled nitric oxide in predicting AHR. These findings highlight its potential as a quick, non-invasive way to rule out AHR, which could simplify asthma diagnosis and reduce the need for lengthy bronchial challenge testing.