CKB and gastric cancer: However, few epidemiological studies have shown conflicting results regarding the association between HBV infection and gastric cancer.28 A previous study using the CKB showed that hepatitis B surface antigen (HBsAg) was associated with an HR of 1.41 (1.11-1.80) for stomach cancer (2157 cases), and the association was further replicated in two other small Chinese studies using polymerase chain reaction or immunohistochemistry test measurements of HBsAg.29 In the present study, we measured HBV e antibody and core antibody levels and both were associated with higher risk of duodenal ulcer.