In the univariate analyses (Table 3), infection was significantly associated with age (OR: 1.032, 95% CI: 1.008-1.056; P = 0.008), smoking (OR: 2.728, 95% CI: 1.365-5.452; P = 0.005), bronchiectasis (OR: 3.906, 95% CI: 1.505-10.137; P = 0.005), Diabetes (OR: 8.216, 95% CI: 2.504-26.958; P = 0.001), stages (OR: 2.616, 95% CI: 1.074-6.372; P = 0.034), CD3+T cell percentage (OR: 0.966, 95% CI: 0.943-0.989; P = 0.005), and CD4+T cell count (OR: 0.999, 95% CI: 0.998-1.000; P = 0.004). This evidence concerns the gene CD4 and infection.