Introduction: The BEIgE study revealed clear underestimation of sensitizations to perennial aeroallergens (PAAs) in patients with severe asthma (SA). Among the most prevalent sensitizations were those against Staphylococcus aureus (StA) toxins, which are not routinely tested in clinical practice. This follow-up analysis describes airway inflammatory characteristics of SA patients exclusively sensitized to one or more StA toxins (?StA-monosensitized? [StA-MS]).

Methods: This prospective study was conducted in 16 centers during a single outpatient consultation in 176 adults with an established diagnosis of SA (GINA 2020, treatment Step 5). Patients treated with omalizumab or maintenance systemic glucocorticosteroids were excluded. Patients were tested for 43 PAAs amongst which StA enterotoxins A-C and Toxic Shock Syndrome Toxin (TSST).

Results: StA-MS patients (n=15) had higher serum total IgE (IgE_tot)(139.3±26.7 vs 34.0±6.9 kU/L*), blood eosinophils (bEOS)(522.8±84.6 vs 287.2±36.7 cells/µL), and FeNO (55.1±10.6 vs 40.2±11.1 ppb) compared to non-sensitized patients (all 43 tests negative)(n=27). StA-MS had similar values compared to sensitized patients with negative StA tests, the latter group (n=62) having serum IgE_tot of 185.3±33.0 kU/L, bEOS 490.8±57.7 cells/µL, and FeNO 37.7±5.4 ppb (all mean±SEM, *p<0.05).

Conclusion: Patients with SA and StA-monosensitization display a ?Type 2? (T2) airways inflammatory profile and may therefore represent a T2 SA subgroup which is incorrectly considered as ?non-sensitized?; testing for StA toxins may therefore be indicated in this group of patients. Further prospective studies are needed to establish whether they might benefit from anti-IgE therapy.