Quantification of total apolipoprotein E and its specific isoforms in cerebrospinal fluid and blood in Alzheimer’s disease and other neurodegenerative diseases

• SRM assay was developed for identification and quantification of apoE isoforms.
• CSF and blood samples were analyzed from AD patients and control subjects.
• The assay allows apoE phenotype determination with 100% accuracy.
• APOE ϵ4 carriers have lower level of apoE in blood independent of clinical diagnosis.

A targeted mass spectrometric assay was developed for identification and quantification of apoE isoforms (apoE2, E3 and E4), and it was utilized for screening of samples from AD patients (n = 39) and patients with other neurodegenerative disorders (n = 38). The assay showed good linearity with LOQ corresponds to total apoE concentration of 0.8 and 40 ng/mL in CSF and plasma/serum, respectively. We identified apoE phenotypes with 100% accuracy in clinical samples. We found strong association between genotypes of the individuals and their apoE levels in blood; ϵ4 allele carriers had significantly lower apoE levels in blood than non-carriers.

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