Background: Several studies have investigated the value of alpha-synuclein assay in the cerebrospinal fluid (CSF) of Alzheimer’s disease (AD) and Dementia with Lewy Bodies (DLB) patients in the differential diagnosis of these two pathologies. However, very few studies have focused on this assay in AD and DLB patients at the MCI stage.
Methods: All patients were enrolled under a hospital clinical research protocol from the tertiary Memory Clinic (CM2R) of Alsace by an experienced team of clinicians. A total of 166 patients were included in this study: 21 control subjects (CS), 51 patients with DLB at the prodromal stage (pro-DLB), 16 patients with DLB at the demented stage (DLB-d), 33 AD patients at the prodromal stage (pro-AD) and 32 AD patients at the demented stage (AD-d). CSF levels of total alpha-synuclein were assessed using commercial enzyme-linked immunosorbent assay (ELISA) for alpha-synuclein (AJ Roboscreen). Alzheimer's biomarkers (t-Tau, P-Tau, Aβ42 and Aβ40) were also measured.
Results: The alpha-synuclein assays showed a significant difference between the AD and DLB groups. Total alpha-synuclein levels are significantly higher in AD patients than in DLB patients. Interestingly is that the levels seem to be altered from the prodromal stage in both AD and DLB. Furthermore, by dividing the patients according to the profiles of Alzheimer's biomarkers typically found or not for each of the two pathologies and then classifying the patients according to the level of alpha-synuclein, we find that alpha-synuclein levels are elevated not only for AD patients with typical “Alzheimer” profile (i.e. 2 or 3 pathological biomarkers) but also for AD patients with a non-typical “Alzheimer” profile (i.e. none or one pathological biomarker).
Conclusions: The modification of total alpha-synuclein levels in the CSF of patients occurs early from the prodromal stage. Moreover, alpha-synuclein assay appears to be of particular interest in the differential diagnosis of AD in cases where the Alzheimer biomarkers do not have a typical profile of the disease, i.e. when there is only one or no pathological biomarker.
Trial registration: ClinicalTrials.gov, (AlphaLewyMa, Identifier: NCT01876459)