Small-Airway Function Variables in Spirometry, Fractional Exhaled Nitric Oxide, and Circulating Eosinophils Predicted Airway Hyperresponsiveness in Patients with Mild Asthma.

PURPOSE

Patients with variable symptoms suggestive of asthma but with normal forced expiratory volume in 1 second (FEV) often fail to be diagnosed without a bronchial provocation test, but the test is expensive, time-consuming, risky, and not readily available in all clinical settings.

PATIENTS AND METHODS

A cross-sectional study was performed in 692 patients with FEV≥80% predicted; normal neutrophils and chest high-resolution computed tomography; and recurrent dyspnea, cough, wheeze, and chest tightness.

RESULTS

Compared with subjects negative for AHR (n=522), subjects positive for AHR (n=170) showed increased FENO values, peripheral eosinophils (EOS), and R5-R20; decreased FEV, FEV/Forced vital capacity (FVC), and forced expiratory flow (FEFs) (≤.001 for all). Small-airway dysfunction was identified in 104 AHR patients (61.17%), and 132 AHR patients (25.29%) (<0.001). The areas under the curve (AUCs) of variables used singly for an AHR diagnosis were lower than 0.77. Using joint models of FEF, FEF, or FEF with FENO increased the AUCs to 0.845, 0.824, and 0.844, respectively, significantly higher than univariate AUCs ( <0.001 for all). Patients who reported chest tightness (n=75) had lower FEFs than patients who did not (<0.001 for all). In subjects with chest tightness, the combination of FEF or FEF with EOS also increased the AUCs substantially, to 0.815 and 0.816, respectively ( <0.001 for all versus the univariate AUCs).

CONCLUSION

FENO combined with FEF and FEF predict AHR in patients with normal FEV. FEF, FEF, or FEF together with EOS also can potentially suggest asthma in patients with chest tightness.