Variables, including sputum purulence, increased sputum volume, diabetes mellitus, FEV1, % predicted, PCT ≥ 0.07 ng/mL, Neu ≥ 6.41 × 10^9/L, CRP ≥ 15.8 mg/dL, OPN ≥ 13.26 ng/mL, and SCS treatment, were retained as covariates in the forward stepwise selection procedure of multivariate analysis. This evidence concerns the gene SPP1 and diabetes mellitus.