A systematic review and meta-analysis of CSF neurofilament protein levels as biomarkers in dementia

Background: Loss of cortical neurons is a key pathological feature in neurodegenerative dementias. Cerebrospinal fluid (CSF) neurofilaments (Nf) are a biomarker for neuronal death and axonal loss. Objective: To perform a meta-analysis to investigate the value of CSF Nf levels for the laboratory-supported differential diagnosis of neurodegenerative dementias. Methods: A systematic review and meta-analysis of studies on CSF Nf heavy (NfH) and light (NfL) levels in patients with dementia. The dementia subgroups analysed were Alzheimer (AD), frontotemporal lobe dementia (IFTILD), vascular dementia (SVID), minimal cognitive deficit (MCI). Results: We identified 12 studies on CSF NfH and NfL levels which met the inclusion criteria and 11 were of a quality good enough to be used in this meta-analysis. CSF data was available on 818 patients (306 AD, 106 SVD, 98 FTLD, 25 MCI, 283 controls). Overall CSF NfH and NfL levels were higher in patients with AD, FTLD and SVD when compared to controls. The size of the effect ranged from 0.71 to 1.38. The strongest effect was observed for the comparison of FTLD patients with controls, both for NfL (1.38) and NfH (0.74).CSF NfL were also able to separate patients with FTLD from those with AD. Conclusion: At present we cannot recommend CSF NfH and NfL levels for use as a screening test in the diagnosis of dementia because of the rather small effect size. However, both neurofilament proteins may be of value for targeted investigation of some patients with FTLD, SVD and AD.