The Role of Fractional Exhaled Nitric Oxide in Diagnosing Asthmatic Type 2 Chronic Rhinosinusitis With Nasal Polyps

Background: Fractional exhaled nitric oxide (FeNO) is useful in the management of asthma and predicting the efficacy of standard corticosteroids and biologics. However, the diagnostic value of FeNO in asthmatic chronic rhinosinusitis with nasal polyps (CRSwNP) remains unclear.

Objective: We assessed FeNO levels in patients with CRSwNP and evaluated the diagnostic value of FeNO for screening type 2 CRSwNP (T2-CRSwNP) with asthma.

Methods: We enrolled 94 patients who were diagnosed with CRSwNP and underwent functional endoscopic sinus surgery. FeNO levels, the blood eosinophil percentage, total IgE, spirometry tests (FEV1/FVC), Lund-Mackay CT score, and percentage of patients with comorbid asthma were compared among CRSwNP subgroups. Spearman rank correlation test was used to assess the degree of association between variables. ROC curve analysis was conducted to evaluate the diagnostic capability to differentiate T2-CRSwNP based on clinical and histological classifications.

Results: FeNO levels and the blood eosinophil percentage were significantly higher in patients with T2-CRSwNP(h) based on histological data ( < .05). FeNO was correlated with the blood eosinophil percentage ( = 0.420,  < .001) and FEV1/FVC ( = -0.324,  = .001). A FeNO level of 27 ppb had a good ability to discriminate patients with asthmatic T2-CRSwNP(h) (AUC = 0.848; 95% CI = 0.7602-0.9361; sensitivity = 90.9%; specificity = 63.9%). The optimal cutoff values for FeNO and the blood eosinophil percentage for diagnosing asthmatic T2-CRSwNP(h) were 68 ppb and 5.6% (sensitivity = 95.5%; specificity = 86.1%; AUC = 0.931; 95% CI = 0.8832-0.9791). In the diagnosis of severe T2-CRSwNP(c) based on clinical data, a FeNO level of 36 ppb showed the highest AUC (0.816; 95% CI = 0.7173-0.914; sensitivity = 72.7%; specificity = 79.2%).

Conclusion: FeNO is a useful marker for screening asthmatic T2-CRSwNP even prior to biopsy or asthma evaluation and may assist in selecting a proper treatment.