Blood-based neurochemical diagnosis of vascular dementia: A pilot study

Blood-based tests for the differential diagnosis of Alzheimer's disease (AD) are under intensive investigation and have shown promising results with regard to A beta 40 and A beta 42 peptide species in incipient AD. Moreover, plasma A beta 40 was suggested as an independent cerebrovascular risk factor candidate. These considerations prompted us to analyse a total of 72 plasma samples in vascular dementias (VAD, n = 15), AD with cerebrovascular disease (AD with CVD, n = 7), AD (n = 15), Parkinson's disease and Parkinson's disease dementia (PD/PDD, n = 20) and 15 patients with depression that served as controls (DC) for distinct plasma amyloid-beta (A beta) peptide patterns. For the analysis of plasma we used immunoprecipitation followed by the quantitative ApSDS-PAGE/immunoblot. For comparison, CSF tau and A beta 1 -42 analyses were performed. The major outcome was an increase in A beta 1-40 in plasma of VAD paralleled by a decrease in the ratio of A beta 1-38/A beta 1-40. The ratio A beta 1-38/A beta-1-40 in plasma enabled contrasts of beyond 85% and 80% for discriminating VAD from DC and all other patients, respectively. In CSF, we confirmed the typical CSF biomarker constellation of increased tau and diminished A beta 1-42 levels for AD. The diagnostic accuracy of plasma A beta 1-38/A beta 1-40 for VAD resembled the accuracy of CSF biomarkers for AD. From the presented results, we consider the ratio of plasma A beta 1-38/ A beta 1-40 peptides to be a blood-based biomarker candidate for VAD.