Plasma neurofilament light chain and phosphorylated tau 181 in neurodegenerative and psychiatric disorders: moving closer towards a simple diagnostic test like a 'C‐reactive protein' for the brain?
Authors: Eratne Dhamidhu , Santillo Alexander , Li Qiao‐Xin , Kang Matthew , Keem Michael , Lewis Courtney , Loi Samantha M , Walterfang Mark , Hansson Oskar , Janelidze Shorena , Yassi Nawaf , Watson Rosie , Berkovic Samuel F , Masters Colin L , Collins Steven , Velakoulis Dennis ,   The MiND Study Group
Published: December 2021

Background

Accurate, timely diagnosis of neurodegenerative disorders, in particular distinguishing primary psychiatric from neurological disorders and in younger people, can be challenging. There is a need for biomarkers to reduce the diagnostic odyssey and improve outcomes. Neurofilament light (NfL) has shown promise as a diagnostic biomarker in a wide range of disorders. Our Markers in Neuropsychiatric Disorders (MiND) Study builds on our pilot (Eratne et al, ANZJP, 2020), to explore the diagnostic and broader utility of plasma and cerebrospinal fluid (CSF) NfL and other novel markers such as phosphorylated tau 181 (p‐tau181), in a broad range of psychiatric and neurodegenerative/neurological disorders, with a view of translation into routine clinical practice.

Methods

We assessed plasma and/or CSF NfL and p‐tau181 concentrations in broad cohorts, including: patients assessed for neurocognitive/psychiatric symptoms at Neuropsychiatry and Melbourne Young‐Onset Dementia services and other services, in a wide range of disorders including Alzheimer disease, frontotemporal dementia, schizophrenia, bipolar disorder, depression, Niemann‐Pick Type C, epilepsy, functional neurological disorders. The most recent primary consensus diagnosis informed by established diagnostic criteria was categorised: primary psychiatric disorder (PPD), neurodegenerative/neurological disorder (ND), or healthy controls (HC).

Results

Findings from over 500 patients/participants will be presented, which indicate that CSF and plasma NfL levels are significantly elevated in a broad range of ND compared to a broad range of PPD, and HC, and bvFTD progressors from phenocopy syndromes, differentiating with areas under the curve of >0.90, sensitivity and specificity >90%. Plasma P‐tau181 levels distinguished Alzheimer disease (mainly younger sporadic), compared to other neurodegenerative disorders, with AUC 0.90, 90% sensitivity and specificity. As recruitment, sample analysis, data collection is ongoing, the most up to date results will be presented.

Conclusions

NfL shows great promise as a diagnostic test to assist with the common, challenging diagnostic dilemma of distinguishing neurodegenerative from non‐neurodegenerative and primary psychiatric disorders. Plasma p‐tau181 shows strong diagnostic utility in younger‐onset Alzheimer disease. A significantly elevated NfL in someone with a psychiatric diagnosis should prompt consideration of neurodegenerative differentials. Plasma NfL could dramatically alter clinical care of patients with neuropsychiatric and neurological symptoms, improving outcomes for patients, their families, the healthcare system, and clinical trials.