Table 2. List of metabolite molecules selected by the Random Forest classifier (AD versus elderly health controls).

Metabolite molecule	Peak height data normalized to whole mean only			Peak ratios normalized to internal standard
	OR	95% CI	P-value	OR	L95 95% CI	P-value
Mass/z 367	0.124	0.03–0.39	1.31E−03	0.115	0.03–0.36	8.09E−04
ChE 32:0	0.251	0.10–0.52	7.51E−04	0.237	0.10–0.48	4.19E−04
ChE 34:0	0.151	0.05–0.38	3.14E−04	0.152	0.05–0.37	2.90E−04
ChE 34:6	0.231	0.08–0.53	1.56E−03	0.126	0.03–0.35	5.40E−04
ChE 32:4	0.141	0.04–0.43	1.75E−03	0.056	0.01–0.24	6.56E−04
ChE 33:6	0.218	0.07–0.55	3.15E−03	0.205	0.06–0.50	2.21E−03
Mass/z 628	3.669	1.20–13.93	3.49E−02	NA	NA	NA
Mass/z 906	0.210	0.07–0.50	1.40E−03	0.226	0.09–0.48	3.73E−04
Mass/z 315	5.084	1.78–16.88	4.12E−03	NA	NA	NA
ChE 40:4	0.362	0.18–0.67	2.56E−03	0.279	0.12–0.55	6.43E−04
Cholesterol	NA	NA	NA	0.316	0.02–5.01	4.21E−01

Abbreviations: AD, Alzheimer's disease; ChE, cholesteryl ester; CI, confidence interval; NA, not available; OR, odds ratio.

Results are presented for peak height and peak ratio (measurement normalized to internal standard) after covariate adjustment. The metabolites are ordered according to their importance during recursive feature elimination. All metabolites except for mass 628 were associated with AD in single analyte regression analysis (q<0.05). Results for semiquantified mass 628 and mass 315 are not presented as they were not consistently above the limit of quantification. Results are also presented for the APOE ɛ4 allele and for cholesterol peak ratio. The association of APOE ɛ4 was OR=5.620, 95% CI=2.27–16.29, P=5.48E−04 per ɛ4 allele.