Most patients with dementia with Lewy bodies (DLB) exhibit diffuse plaque–only pathology with rare neocortical neurofibrillary tangles (NFTs), as opposed to the widespread cortical neurofibrillary-tau involvement in Alzheimer disease (AD). Another pathological difference is the astrocytic and microglial inflammatory responses, including release of interleukins (ILs), around the neuritic plaques and NFTs in AD brains that are absent or much lower in DLB. We analyzed cerebrospinal fluid (CSF) markers that reflect the pathological differences between AD and DLB.
To determine CSF concentrations of tau, β-amyloid, IL-1β, and IL-6 as potential diagnostic clues to distinguish between AD and DLB.
We measured total tau, β-amyloid1-42, IL-1β, and IL-6 levels in CSF samples of 33 patients with probable AD without parkinsonism, 25 patients with all the core features of DLB, and 46 age-matched controls.
Patients with AD had significantly higher levels of tau protein than patients with DLB and controls (P<.001). The most efficient cutoff value provided 76% specificity to distinguish AD and DLB cases. Patients with AD and DLB had lower, but not significantly so, β-amyloid levels than controls. The combination of tau and β-amyloid levels provided the best sensitivity (84%) and specificity (79%) to differentiate AD vs controls but was worse than tau values alone in discriminating between AD and DLB. β-Amyloid levels had the best correlation with disease progression in both AD and DLB (P = .01). There were no significant differences in IL-1β levels among patients with AD, patients with DLB, and controls. Patients with AD and DLB showed slightly, but not significantly, higher IL-6 levels than controls.
The tau levels in CSF may contribute to the clinical distinction between AD and DLB. β-Amyloid CSF levels are similar in both dementia disorders and reflect disease progression better than tau levels. Interleukin CSF concentrations do not distinguish between AD and DLB.