Neurofilaments and tau proteins in cerebrospinal fluid and serum in dementias and neuroinflammation.

AIMS The aim of this study was to evaluate the diagnostic potential of cerebrospinal fluid (CSF) and serum levels of neurocytoskeletal proteins and their ratios for the diagnosis of dementias and to assess the differences in neurocytoskeletal proteins between neurodegeneration and neuroinflammation. METHODS CSF and serum levels of neurofilament light subunits (NFL) and neurofilament heavy subunits (NFH) as well as CSF levels of total tau (t-tau) and phosphorylated tau (p-tau) proteins were determined using ELISA in 20 Alzheimer's disease patients (AD group), 13 patients with other dementias (OD group), 17 patients with inflammatory aseptic neuro-infections (IP), and 20 aged-matched cognitively normal elderly persons (NC group). RESULTS The ratio CSF p-tau/t-tau was significantly higher in the NC group than that in the AD or OD groups (P<0.0005 for each group). The CSF NFH/p-tau and CSF NFL/p-tau ratios were significantly lower in AD patients than OD patients (P≤0.003). Serum and CSF NFL and CSF NFH levels were significantly higher in OD patients than AD patients (P≤0.03). The lowest values of the CSF NFL/NFH ratio were found in the IP group and they significantly differed from those in normal controls (P<0.0001) and any dementia group (IP vs. AD P<0.0001; IP vs. OD P=0.03). CONCLUSION CSF tau proteins and their index differentiated between AD or OD patients and cognitively normal subjects, while CSF levels of neurofilaments expressed as their index seem to contribute to the discrimination between patients with neuroinflammation and normal controls or AD patients.