Fixed airway obstruction and bronchodilator responsiveness phenotypes in severe asthma population from SANI registry

Among 354 patients, 190 (53.7%) reported AO with 116 (60.1%) resulting in FAO. The overall FAO rate at enrolment was 32.8%. Compared with BDR, FAO patients had better asthma control (34.5% vs 20.3%, p=0.004), a higher ACT (17.4 vs 15.2, p=0.005) and AQLQ (4.6 vs 3.8, p=0.001) score. FAO patients were less likely to visit the emergency room or be hospitalised than BDR (p=0.050), with no difference in AEs. The effect of airway calibre on fractional exhaled nitric oxide is more likely to cause its lower level within FAO compared with BDR (29.5 vs 46.0 ppb, p=0.04) than a lower T2 burden. A variation from FAO to BDR or no-AO was associated with the Global Initiative for Asthma classification (step 4 vs 5: HR 3.58 (95% CI 1.16 to 11.03)) and the age of asthma onset (30-39 vs <20 years: HR 3.94 (95% CI 1.09 to 14.30)) CONCLUSION: Stratifying SA patients from the SANI registry reveals an FAO phenotype that expresses different clinical outcomes and biological markers compared to BDR. Over time, FAO may be reversible in late-onset SA with less inhaled corticosteroid treatment.