MUC5AC and biliary tract cancer: 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.