The RF-Boruta confirmed 10 important predictors, ILA, IAA ME, isobutyric acid, 2-methylbutyric acid, age, MMSE score, homozygous APOE-ɛ4 vs none, widowed vs. single, serotonin, and tryptophan, as discriminating AD cases from non-cases (Fig. 3B). Here, APOE is linked to Alzheimer disease.