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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