Persistent airway inflammation common in asthmatics despite medication use
Airway type 2 inflammation remains persistent in many asthmatics on inhaled corticosteroids (ICS), a new study has shown. These patients tend to be older and have a more severe disease.
Using quantitative polymerase chain reaction, researchers measured expression levels of interleukins (IL) 4, 5 and 13 induced sputum samples collected from 259 asthmatic adults on ICS medication. Thirty healthy adults (mean age 38.0±13.1 years; 60 percent female) were also included as controls.
Expression levels of IL-4, IL-5 and IL-13 cytokines were significantly elevated in asthmatics than in healthy controls. The same was true for the type 2 gene mean (T2GM), which was the average gene expression of all three cytokines and functioned as a composite metric of airway type-2 gene expression.
Triamcinolone injection produced no significant effect on the expression levels of IL-4, IL-5 and IL-13. The resulting change in the T2GM was minimal, decreasing only by an average of 3 percent and not achieving statistical significance (p=0.19).
Using the 50th centile of T2GM values as a cutoff, researchers identified 130 asthmatics (74 percent female) with refractory type 2 inflammation despite ICS treatment. The remaining 129 (63 percent female) were designated as steroid-treated. Those in the former vs latter group tended to be older (mean, 50.3±14.0 vs 46.2±13.7 years; p=0.02).
The interaction between age and T2GM was further confirmed in a subsequent analysis where researchers divided the asthmatic participants into age quintiles. They found that T2GM values were significantly higher in older vs younger age quintiles.
Disease severity also appeared to play an important role in persistent inflammation. Those with high T2GM values had lower forced expiratory volume in 1 second values (69.5±17.9 percent vs 76.1±19.2 percent; p<0.001) and were more likely to be diagnosed with severe asthma (74 percent vs 62 percent).