Molecular T2 asthma phenotypes are stable but heterogeneous: the usefulness of periostin for endotyping.

Background: The stability of molecular T2/non-T2 phenotypes remains uncertain. The objectives of this study were to assess the stability of these phenotypes and the correlation between serum periostin and asthma T2 phenotypes and endotypes.

Methods: Demographics, clinical data, and blood samples were collected. Patients diagnosed with moderate-to-severe asthma were classified into T2 or non-T2 according to previously defined thresholds of blood eosinophilia and serum total IgE levels. Asthma endotype was also determined. After at least 1 year of follow-up, the stability of T2 phenotypes and endotypes was assessed.

Results: A total of 53 patients (72% women), mean age 47 years (range 16-77), were included. In the initial and second evaluations, the T2 phenotype was found in 41.5% and 43.4% of patients and the non-T2 phenotype was found in 58.4% and 56.7%, respectively. The mean [standard deviation (SD), range] serum periostin level was 52.7 (26.2, 22.6-129.7) ng/mL in patients with T2 phenotype, and 39.3 (25.6, 7.7-104.) ng/mL in non-T2 patients ( = 0.063). Periostin levels correlated to endotypes ( = 0.001): 45.7 (27.9) ng/mL in allergic asthma ( = 16 patients), 64.7 (24.9) in aspirin-exacerbated respiratory disease ( = 14), 59.0 (27.6) ng/mL in late-onset eosinophilic asthma ( = 4), and 28.3 (13.3) ng/mL in non-eosinophilic asthma ( = 18).

Conclusions: T2 and non-T2 asthma phenotypes assessed by accessible methods in daily practice are stable over time yet widely heterogeneous. Serum periostin does not discriminate between T2 and non-T2 phenotypes. Nevertheless, its correlation to asthma endotypes may contribute to guide therapies targeting T2 cytokines in a more personalized approach.