Figure 4 illustrates the association of heme, HO-1, Hp, and Hx, respectively, with asymptomatic infection. Heme: AUC 0.80 P < 0.0001, HO-1: AUC 0.63 P = 0.028, Hp: AUC 0.62 P = 0.027, and Hx: AUC 0.81 P < 0.001 (Figure 4). This evidence concerns the gene HP and infection.