Differential levels of alpha-synuclein, beta-amyloid42 and tau in CSF between patients with dementia with Lewy bodies and Alzheimer's disease.

BACKGROUND: The clinical diagnosis of dementia with Lewy bodies (DLB) is made on the basis of consensus criteria; however, the sensitivity of the criteria is relatively low. There are no generally accepted biomarkers to distinguish DLB from other dementias. Here the utility of quantification of alpha-synuclein, beta-amyloid42 (Abeta42) and tau in the CSF of patients with DLB, Alzheimer's disease (AD) and other dementias was examined.

METHODS: 86 patients were divided into three age and sex matched groups: DLB (n=34), AD (n=31) and other dementias (n=21). Two patients with alpha-synuclein gene (SNCA) duplication were also examined. Abeta and tau were quantified using an ELISA kit. A modified sandwich ELISA was developed which enables the sensitive quantification of CSF alpha-synuclein.

RESULTS: Total and phosphorylated tau levels as well as Abeta40/42 and tau/Abeta42 ratios were significantly higher in AD patients than in patients with DLB (p<0.01) and other dementias (p<0.01). CSF alpha-synuclein levels in DLB patients were significantly lower than those in patients with AD (p<0.05) and other dementias (p<0.01). CSF alpha-synuclein level correlated with the Abeta42 level in DLB patients (p=0.01, r=0.43). Two patients with SNCA duplication exhibited relatively low levels of CSF alpha-synuclein.

CONCLUSIONS: The study suggests that reduced levels of CSF alpha-synuclein in DLB may reflect the accumulation of alpha-synuclein with Lewy pathology in the brain and that quantification of CSF alpha-synuclein helps in the differentiation of DLB from AD and other dementias in combination with Abeta42 and tau analysis.