When factors associated with YKL-40 were included in a multivariate regression analysis, the associations between serum YKL-40 and SNP (131 C/G) (p<0.001), smoking (p<0.001), asthma severity (GINA 1–4, p=0.001), and BMI (p<0.01) remained statistically significant. This evidence concerns the gene CHI3L1 and asthma.