A previous clinical study demonstrated that serum DPP4 levels were elevated in asthma patients, regardless of whether they were using inhaled corticosteroids, compared to healthy control groups.[9] However, another study revealed that serum DPP4 levels in asthma patients were lower than those in healthy control groups, especially among patients with severe asthma taking inhaled corticosteroids.[39] Hence, current clinical research findings regarding the expression of serum DPP4 in asthma patients are inconclusive. This evidence concerns the gene DPP4 and asthma.