GPC1 and gallbladder carcinoma: The levels of serum GPC1 could distinguish PDAC from gallbladder carcinoma (P < 0.001), colorectal carcinoma (P < 0.001), gastric carcinoma (P < 0.001), and prostate cancer (P < 0.001), but could not differentiate PDAC from hepatocellular carcinoma (P = 0.395) and cholangiocarcinoma (P = 0.724).