Expression of Salivary Metabolite Markers in Serum
Given the 106 characteristic metabolites previously studied in salivary metabolic profiling,18 the extent of their changes in serum between OSCC and HC group were investigated. For this inter-specimen validation purpose only, the serum samples from two cohorts were combined to implement the rank-sum test. As a result, 52 out of 106 metabolites discovered in the previous saliva metabolomics were found to remain at abnormal levels in serum (Table S4 ), although changes in serum for most of these metabolites were not as obvious as those in saliva. Moreover, 33 out of these 52 metabolites in serum showed the same change trends with these in saliva (OSCC vs HC). Altogether, there were 65 metabolites discovered to be changed in OSCC compared to HC with statistical significance (FDR < 0.05)). These metabolites were treated as serum marker candidates that have the potential discrimination powers for OSCC screening model development.