Extended nitric oxide analysis in patients with suspected airway hyperreactivity

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 noninvasive 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.

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).

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 cutoffs provided strong negative predictive values, but their positive predictive values were low.

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, noninvasive way to rule out AHR, which could simplify asthma diagnosis and reduce the need for lengthy bronchial challenge testing.