The clinical distinction between Alzheimer`s disease (AD) and dementia with Lewy bodies (DLB) is sometimes difficult, particularly in mild cases. Although CSF markers such as amyloid beta42 (Abeta42) and P-tau can distinguish between AD and normal controls, their ability to distinguish between AD and DLB is not adequate.
OBJECTIVE: This study aims to investigate whether CSF markers, in particular levels of Abeta38, can differentiate between mild AD and DLB.
METHODS: 85 individuals were included after standardised diagnostic procedures: 30 diagnosed as probable AD, 23 probable DLB, 20 probable Parkinson`s disease dementia and 12 non-demented control subjects. CSF levels of Abeta38, Abeta40 and Abeta42 were determined using commercially available ultra-sensitive multi-array kit assay (MSD) for human Abeta peptides. Total tau (T-tau) and phosphorylated tau (P-tau) were analysed using ELISA (Innotest). In addition, combinations (Abeta42/Abeta38, Abeta42/Abeta40, Abeta42/P-tau and Abeta42/Abeta38/P-tau) were assessed.
RESULTS: Significant between group differences were found for all CSF measures, and all except Abeta40, Abeta42 and Abeta42/P-tau differed between AD and DLB. The Abeta42/Abeta38 ratio was the measure that best discriminated between AD and DLB (AUC 0.765; p<0.005), with a sensitivity of 78% and a specificity of 67%.
CONCLUSION: This study suggests that the level of Abeta38 can potentially contribute in the diagnostic distinction between AD and DLB when combined with Abeta42. Single measures had low diagnostic accuracy, suggesting that developing a panel of markers is the most promising strategy. Studies with independent and larger samples and a priori cut-offs are needed to test this hypothesis.

source: journal of neurology, neurosurgery and neuropsyciatry