A subgroup analysis revealed that YKL-40 expression was higher in both severe and moderate asthma than mild asthma (41.0% [35.8-44.7%] vs. 19.2% [14.6-20.8%]; p < 0.001 and 29.2% [24.4-33.3%] vs. 19.2% [14.6-20.8%]; p < 0.001, respectively). Here, CHI3L1 is linked to asthma.