Baseline dual elevation of fractional exhaled nitric oxide and blood eosinophils is associated with clinical remission in severe eosinophilic asthma treated with biologics: a real-world prospective study

Background: Clinical remission on biologic treatment has emerged as a relevant target in severe asthma management. Simple and widely available type 2 (T2) biomarkers, such as fractional exhaled nitric oxide (FeNO) and blood eosinophil count (BEC), may help stratify patients in real-world practice. Objective: To explore whether the combined baseline assessment of FeNO and BEC is associated with clinical remission at 12 months in patients with severe eosinophilic asthma (SEA) treated with biologic therapy. Methods: In this prospective real-world single-center study, 69 patients with severe asthma initiating benralizumab (n = 26), mepolizumab (n = 16), or dupilumab (n = 27) were enrolled. At baseline, patients were classified as dual high biomarker T2 (DHB-T2: FeNO50 ≥ 25 ppb and BEC ≥300 cells/µL) or heterogeneous/no biomarker T2 (HNB-T2: all other biomarker combinations). Clinical remission at 12 months was defined by the simultaneous fulfilment of the following criteria: absence of maintenance oral corticosteroids, zero exacerbations, FEV1 ≥ 80% predicted, and Asthma Control Test (ACT) score ≥20. Results: At 12 months, 42 of 69 patients (60.8%) achieved clinical remission. DHB-T2 status was associated with a higher likelihood of remission (univariate OR 4.58, p = 0.005; multivariate OR 12.67, p = 0.002). The DHB-T2 classification showed a sensitivity of 73.33% and a specificity of 62.45% for identifying patients achieving remission. Isolated baseline elevation of either FeNO or BEC alone was not associated with clinical remission. Conclusions: In this real-world cohort of patients with severe eosinophilic asthma treated with biologics, concomitant baseline elevation of FeNO and blood eosinophils was associated with a higher likelihood of achieving clinical remission at 12 months.