AFP and hepatocellular carcinoma: OPLS-DA was further used to analyze the metabolic differences among the AFP+HCC with healthy groups (Figure 2C for C18 column, Figure 2D for HILIC columns), AFP–HCC with healthy groups (Figure 2E for C18 column, Figure 2F for HILIC columns), HBG with healthy groups (Figure 2G for C18 column, Figure 2H for HILIC columns).