Lung function provides better insight into the sex-related differences among severe asthmatics than biomarkers.

In severe asthma, a sex-oriented diagnostic and therapeutic approach is lacking, and, lung function tests have been generally limited to FEV1 assessment, irrespective of the underlying pathophysiology of the disease itself. We retrospectively investigated sex-specific anthropometric, clinical, biological, and functional characteristics in 111 patients (63 females) severe asthmatics referred to the Severe Asthma Outpatients Clinic from 2015 to 2019. In each patient data of clinical history, lung function (i.e. spirometry, plethysmographic lung volumes, alveolar and central FeNO, forced oscillometry), asthma control (ACT) and quality of life (AQLQ), and biomarkers (serum total IgE and eosinophil count) were collected. Comparisons of continuous and categorical variables between males and females were assessed by means of two-sided t-tests and Fisher exact test, respectively. Clinical history data and biomarkers were similar between males and females except ASA hypersensitivity that was more prevalent (P<0.05) in females. Spirometry data were also similar between sexes. In contrast, females showed higher (P<0.05) FRC, RV, TLC and alveolar FeNO values than males. Forced oscillometry assessment revealed that resistance at 5 and 20 Hz were higher and reactance at 5 Hz lower in females than males. Sex-related differences in lung anatomy could explain the higher hyperinflation of female patients. The concurrent higher alveolar FeNO with increased resistances and lower reactance may suggest a higher degree of peripheral airways inflammation in females. A complete lung function evaluation may reveal the, more extensive lung involvement of female patients with severe asthma.