Therefore, the aims of this study were: (a) the implementation of qualitative apoE phenotyping into our quantitative apolipoprotein LC-MS/MS assay; (b) the investigation of relationships between total apoE plasma concentrations and apoE phenotypes in patients with stable coronary artery disease and patients with mild cognitive impairment; (c) the evaluation of effects of apoE phenotypes on different plasma apolipoprotein and lipid species. The gene discussed is APOE; the disease is coronary artery disorder.