Blood tryptase and thymic stromal lymphopoietin levels predict the risk of exacerbation in severe asthma

Abstract

Some patients with severe asthma experience exacerbations despite receiving multiple therapy. The risk of exacerbation and heterogeneous response to treatment may be associated with specific inflammatory molecules that are responsive or resistant to corticosteroids. We aimed to identify the independent factors predictive for the future risk of exacerbation in patients with severe asthma. In this multi-center prospective observational study, 132 patients with severe asthma were enrolled and divided into exacerbation (n = 52) and non-exacerbation (n = 80) groups on the basis of exacerbation rate after a 1-year follow-up period. We found that previous history of severe-to-serious exacerbation, baseline blood eosinophil counts (≥ 291cells/μL), and serum tryptase (≤ 1448 pg/mL) and thrymic stromal lymphopoietin (TSLP) levels (≥ 25 pg/mL) independently predicted the future development of exacerbation with adjusted odds ratios (AOR) of 3.27, 6.04, 2.53 and 8.67, respectively. Notably, the patients with high blood eosinophil counts and low tryptase levels were likely to have more exacerbations than those with low blood eosinophil counts and high tryptase levels (AOR 16.9). TSLP potentially played the pathogenic role across different asthma phenotypes. TSLP and tryptase levels may be implicated in steroid resistance and responsiveness in the asthma inflammatory process. High blood eosinophil counts and low serum tryptase levels predict a high probability of future asthma exacerbation.

Figure 1

Kaplan–Meier curves of the cumulative probability of exacerbation during the 1-year follow-up period stratified by previous history of asthma exacerbation (A), serum tryptase (B) and TSLP (C) levels, and blood eosinophil count (D). The cut-off values of 1448 pg/mL, 25 pg/mL, and 291 cells/µL for serum tryptase level, serum TSLP level, and blood eosinophil count, respectively, were chosen by receiver operating characteristic curve analysis.

Figure 2

Adjusted odds ratio (AOR) for developing asthma exacerbation during the 1-year follow-up period based on blood tryptase and eosinophil levels. High (H) and low (L) levels of serum tryptase and blood eosinophil count were defined on the basis of the cut-off values of 1448 pg/mL and 291 cells/µL, respectively. * denotes p value < 0.05. When G1 group is defined as reference, the AOR with 95% confidence intervals (95% CI) and p value for asthma exacerbation during the 1-year follow-up period for G4, G3, and G2 are 16.92 (3.88–73.74, p < 0.001), 9.67 (2.26–41.34, p = 0.002), and 7.25 (1.97–26.63, p = 0.003), respectively.