Targeted quantification in the validation set
After untargeted metabolomics analysis, 40 differential metabolites were selected to perform quantification in patients in the validation set. Metabolites were assayed in multiple reaction monitoring (MRM) mode by LC-MS/MS using an EXION LC System (SCIEX) coupled with SCIEX 6500 QTRAP + Triple Quadrupole mass spectrometry (SCIEX). Details were described in the supplementary material.