Diagnostic value of fractional exhaled nitric oxide combined with small airway function test for chronic cough / 中国基层医药

ABSTRACT

Objective:To investigate the value of fractional exhaled nitric oxide (FeNO) combined with small airway function test to replace bronchial provocation test and induced sputum test in differentiating cough variant asthma (CVA) from eosinophilic bronchitis (EB).Methods:The clinical data of 105 patients with chronic cough admitted to The Third People's Hospital of Hubei, Jianghan University from January 2018 to December 2021 were retrospectively analyzed. These patients consisted of 40 patients with CVA (CVA group), 25 patients with EB (EB group), and 40 patients with other chronic coughs (other chronic cough group). FeNO and lung function were compared between groups. The value of FeNO, small airway function, and their combination in differentiating CVA from EB were analyzed using the receiver operating characteristic curves.Results:FeNO level was the highest in the CVA group [33.0 (30.0, 37.8) ppb], followed by the EB group [28.0 (25.5, 32.0) ppb], and the lowest in other chronic cough group [13.0 (11.0, 15.0) ppb]. There was significant difference in FeNO level between groups ( H value = 79.00, P < 0.05). There were no significant differences in forced vital capacity (FVC), forced expiratory volume in 1 second (FEV 1), FEV 1/FVC, peak expiratory flow (PEF) between groups (all P > 0.05). Maximal mid-expiratory flow (MMEF) [74 (66.0, 77.4) in the CVA group, 80 (79.0, 83.3) in the EB group, 88.0 (86.4, 90.0) in other chronic coughs group], FEF25 (%) [70.0 (60.3, 75.1) in the CVA group, 78.0 (74.1, 85.0) in the EB group, 81.7 (78.9, 86.3) in other chronic coughs group], FEF50 (%) [75.2 (67.1, 80.8) in the CVA group, 80.6 (75.7, 85.9) in the EB group, 89.4 (87.0, 90.5) in other chronic coughs group], FEF75 (%) [76.4 (68.7, 85.8) in the CVA group, 80.9 (77.4, 89.7) in the EB group, 90.8 (87.2, 94.2) in other chronic coughs group] were significantly lower in the CVA group than those in other chronic coughs group. With the exception of FEF25 (%), MMEF (%), FEF50 (%), and FEF75 (%) were significantly lower in the EB group compared with other chronic coughs group. MMEF (%) and FEF25 (%) in the CVA group were significantly lower compared with the EB group. There were significant differences in MMEF (%), FEF50 (%), and FEF75 (%) between groups ( H = 62.82, 47.04, 47.41, 49.11, all P < 0.01). There were significant differences in FEF50 (%) and FEF75 (%) between CVA and EB groups (both P > 0.05). In binary logistic regression equation, FeNO and MMEF (%) were important indexes to distinguish CVA from EB ( P < 0.05). Bronchial provocation test and induced sputum test were used as the gold standard to distinguish CVA from EB. When FeNO and MMEF (%) were used separately to distinguish CVA from EB, the optimal threshold value was 30.0 ppb and 77.7 respectively, the area under the receiver operating characteristic curve was 0.77 and 0.82 respectively, the diagnostic sensitivity was 70% and 77.5% respectively, and the diagnostic specificity was 72% and 88% respectively. When FeNO and MMEF (%) were used in combination to distinguish CVA from EB, the area under the receiver operating characteristic curve was 0.89, and the diagnostic sensitivity and specificity was 75% and 96% respectively. Conclusion:FeNO and MMEF (%) can be used to distinguish CVA from EB. FeNO combined with MMEF (%) has a higher value in distinguishing CVA from EB than FeNO and MMEF alone.