The prevalence of subtypes of type-2 inflammation in a real-life population of patients with difficult-to-control asthma

<b>Introduction:</b> The emergence of differently targeted therapies within type-2 high asthma has highlighted the necessity to identify the level of co-expression of these different pathways. Eosinophilia is considered a marker for IL-5 targeted therapy, while both FeNO and IgE are proposed markers for IL-4/13 targeted therapy. With this study we aimed to assess the co-expression of type-2 biomarkers in patients with difficult-to-control asthma. <b>Methods:</b> Ninety-three patients with difficult-to-control asthma according to ERS/ATS guidelines were recruited for a systematic evaluation across four Danish outpatient clinics. Eosinophilia was defined as ≥3% in sputum or ≥0.3 x 109/L in blood, elevated FeNO as ≥25 ppb, and elevated IgE as ≥150 UI/mL <b>Results:</b> In total, 70% had at least one increased type-2 biomarker: 42% had eosinophilia, 43% had elevated FeNO and 41% had increased IgE, with significant overlaps as illustrated in Figure 1. The proportion of patients who only had one increased type-2 biomarker was 31%; eosinophilia was observed in 10%, FeNO in 12% and IgE in 9%. About one-third (30%) had no elevated Type-2 biomarkers. <b>Conclusion:</b> Among patients with difficult-to-treat asthma, there was a large degree of co-expression of type 2 inflammatory markers, but a significant proportion of patients had isolated increases in only one of these markers, supporting the existence of different subtypes of type-2 asthma.