To assess differences in H. pylori carriage and colonization density upon cancer development and to examine factors that contribute to the observed variability in H. pylori loads in stool, including H. pylori load in the stomach and cagA status, we applied the quantitative ddPCR assays to gastric mucosal brushing samples and stool samples collected from gastric cancer and non-cancer subjects from China. The gene discussed is S100A8; the disease is cancer.