Trend map of differential metabolites in urine (blue) and serum (red) between LUPM and HUPM patients. Horizontal axis represents metabolites, and vertical axis represents fold change between HUPM and LUPM (HUPM/LUPM). The bar above zero axis means the concentration of this metabolite is higher in HUPM patients than in LUPM patients. The bar below zero axis means the concentration of this metabolite is higher in LUPM patients than in HUPM patients. If the metabolite was not significantly changed between LUPM and HUPM patients, it was blank. Fold change was calculated as binary logarithm of average mass response (normalized peak area) ratio between HUPM and LUPM patients, where the positive value means that the average mass response of the metabolite in the HUPM group is larger than that in the LUPM group. All of these differential metabolites were classified to 5 groups according to their change trend in urine and serum.