Table 2. Key metabolites emerged from the search on the metabolome databases: PTD Group vs TD Group.

Group	RT	m/z	Adduct	Mass error (ppm)	AUC ROC (CI 95%)	Sp	Se	Putative metabolites or Metabolite class	Fragmentation pattern
PTD Group	2.23	109.0292	[M-H]-	2	0.55–0.99	0.70	0.82	Muconic dialdehyde	No fragment
	5.06	197.0808	[M-H]-	2.5	0.60–1.00	0.70	0.82	Dicarboxylic unsaturated fatty acid	153.0921, 135.0815, 111.0451
	6.63	421.1606	[M-H]-	7	0.63–1.00	0.70	0.82	Amino acid chain	No fragment
	5.06	179.0699	[M-H]-	8	0.59–0.97	0.60	0.91	3-Methoxybenzenepropanoic acid	No fragment
	5.05	153.092	[M+H]+	6	0.67–1.00	0.70	0.82	4-hydroxynonenal alkyne	No fragment
	0.76	128.0711	[M+H]+	3	0.53–0.96	0.80	0.64	Hydropyridine	No fragment
TD Group	5.28	744.5888	[M+H]+	1	0.61–1.00	1.00	0.64	Phosphatidylcholine	No fragment

RT = Retention Time; m/z = mass-to-charge ratio; ppm = part per million; AUC = Area under the Curve; ROC = receiver operating characteristics; Sp = specificity; Se = sensitivity; the optimal threshold used for specificity and sensitivity is the point closest to the top-left part of the plot with perfect sensitivity or specificity.