Interleukin-33 and soluble ST2 as indicators in patients with asthma

Background. Asthma is a chronic airway inflammatory disorder that differs in the clinical expression and is frequently accompanied by acute attacks. There has been increasing interest on the IL-33/ST2 axis due to its pivotal role in airway inflammation type 2. Whereas IL-33 facilitates inflammatory action, a soluble receptor sST2 can negate this action. In spite of existing biomarkers, there is still a clinically difficult situation in differentiating stable asthma and exacerbation and more valid biomarkers are required. Objectives. The objectives of the case-control study were to determine the difference in serum IL-33 and sST2 between patients with exacerbated asthma, patients with healthy asthma, and healthy controls. Another aim was to determine whether IL-33/sST2 ratio has better discriminatory ability than either of the two. Methods and materials. In this case-control study, 134 individuals were involved comprising 50 acute asthma exacerbation patients, 44 clinically stable asthma patients and 40 healthy controls. The interleukin-33 (IL-33), soluble ST2 (sST2), and the IL-33/sST2 ratio were determined using an enzyme-linked immunosorbent assay (ELISA). Moreover, diagnostic utility of each biomarker and the ratio of IL-33/sST2 was assessed with receiver operating characteristic (ROC) curve analysis to to determine their ability to differentiate exacerbated asthma and stable disease. Results. The levels of serum IL-33 were lowest in the group of healthy controls (25 ± 5 pg/mL), higher in patients with stable asthma (60 ± 15 pg/mL), and highest in patients with exacerbated asthma (95 ± 20 pg/mL), and the differences were significant (p < 0.001). On the same note, the levels of sST2 in asthma patients were higher, and they were 150 ± 30 pg/mL in controls, and 350 ± 60 pg/mL in stable asthma and 600 ± 100 pg/mL in exacerbated asthma. The IL-33/sST2 ratio was different among groups of studies. ROC analysis had revealed that IL-33/sST2 ratio could better discriminate exacerbated and stable asthma, than either IL-33 or sST2. Conclusion. The ratio IL-33/sST2 could add value to distinguishing between the exacerbated and stable asthma and may be useful in the clinical evaluation of the disease activity. Nonetheless, further and bigger research and longitudinal studies are required to prove its utility, until it can be implemented in standard clinical practice.