Third, to clarify the prognostic value of mucin 5ac expression detection methods, we found statistical significance in the IHC (pooled HR: 1.43, 95%CI: 1.053–1.944, P = 0.022) and IB (pooled HR: 2.47, 95%CI: 1.508–4.050, P < 0.001) subgroups, but we should also note that as the 3 studies that did not use IHC were all performed in biliary tract cancer patients, it is hard to draw conclusions about the IB subgroup. Here, MUC5AC is linked to biliary tract neoplasm.