Background T2 biomarkers have been shown to predict responsiveness to corticosteroids and possibly relate to asthma exacerbations and control. T2 biomarkers in the form of fraction exhaled nitric oxide (FeNO), peripheral blood eosinophils (PBE), and serum periostin are easier to measure and probable surrogate markers for induced sputum eosinophilia (ISE). The relationships between PBE, FeNO and periostin particularly in refractory asthma have been conflicting. A composite score of T2 biomarkers has also been postulated to predict exacerbations and may be more sensitive.1
Aim To explore the relationship between the T2 biomarkers individually, and in the form of composite score to asthma exacerbations and control.
Methods Unselected consecutive patients with confirmed diagnosis of refractory asthma (ATS) attending a tertiary severe asthma centre were recruited following an informed consent. Participants were evaluated for the followings: demographics, exacerbations requiring corticosteroids in the preceding 12 months, asthma control questionnaire (Juniper ACQ7), lung function, FeNO, PBE, and periostin measurement. The composite T2 score of all the 3 biomarkers was calculated as previously reported (reference). Statistical analyses were conducted using MedCalc software.
Results One-hundred and fifteen patients were recruited with mean age 45 yrs, 88 (69.8%) females, mean inhaled corticosteroids (BDP equivalent) = 1,647 µg/day, on maintenance OCS = 63 (55%), mean FEV1 = 2.0 L (SD1.8–2.1), FEV1% pred = 68%, and mean FEV1/FVC ratio = 71% (SD = 68–74).
A significant positive correlation between FeNO and PBE was observed (r = 0.39, p = 0.004), but not with periostin. Only FeNO significantly correlated to exacerbations (r = 0.42, p = 0.0008) and only periostin correlated significantly to ACQ7 score (r = 0.33, p = 0.0053). In addition, the biomarkers composite score significantly correlated with exacerbations (r = 0.4, p = 0.0031) (Figure 1), but not ACQ7.
Conclusion In real life settings, FeNO correlated with historical exacerbations and the T2 composite score displayed a dose response correlation with exacerbations frequency. Periostin correlated with ACQ7 but not exacerbations. Further research is required to confirm these findings.
Reference 1 Heaney LG, et al. Thorax 2015;0:1–3. doi:10.1136/thoraxjnl-2015-207326