Fig. 4

PLS-DA variable importance projection (VIP) scores. The metabolites responsible for the classification of VI or not would be identified using the variable importance in projection (VIP) scores. Metabolites with high VIP are more important in providing class separation, while those with small VIP provide less contribution [22]. Formate had the highest VIP score in terms of VI. Red or green on the right of Fig. 4 indicated the low or high concentration of metabolites by comparing the concentration of each metabolite in patients with (1) or without (0) vascular invasion