Discovery and Validation of Serum Metabolite Markers
The rank sum test was employed to search for low abundance
discriminating ions. In the development cohort, there were 241
significantly changed ions in OSCC compared to the HC (FDR <
0.05). When the same procedure was conducted in the validation cohort,
218 ions were found to have significant differences. After overlapping
the two batches of discriminating ions, 65 ions were confirmed to not
only have statistical significance but also to become upregulated or
downregulated in the same direction (Fig. 2A ). After removing
ions that either were redundant or failed to meet the fold change
criteria (larger than 1.5 or smaller than 0.67),
39 metabolites were finally
selected as potential characteristic marker candidates (Table
S3 ). A volcano graph highlighted the top 10 metabolites with the most
obvious fold changes (Fig. 2B ), which shows that lipid
molecules are the predominant species in the serum including
glycerophosphocholine (GPC), lyso-glycerophosphocholine (Lyso-GPC), acyl
carnitine, diacylglycerol (DG), sphingolipids (e.g.,
sphingosine-1-phosphate). Figure 2C displays the relative
expressions of these top 10 metabolites in the form of a heatmap.