Exploiting the role of CSF NfL, CHIT1, and miR-181b as potential diagnostic and prognostic biomarkers for ALS.

Amyotrophic lateral sclerosis (ALS) is a rare neurodegenerative disorder characterized by relentless and progressive loss of motor neurons. A molecular diagnosis, supported by the identification of specific biomarkers, might promote the definition of multiple biological subtypes of ALS, improving patient stratification and providing prognostic information. Here, we investigated the levels of neurofilament light chain (NfL), chitotriosidase (CHIT1) and microRNA-181b (miR-181b) in the cerebrospinal fluid (CSF) of ALS subjects (N = 210) as well as neurologically healthy and neurological disease controls (N = 218, including N = 74 with other neurodegenerative diseases) from a large European multicentric cohort, evaluating their specific or combined utility as diagnostic and prognostic biomarkers. NfL, CHIT1 and miR-181b all showed significantly higher levels in ALS subjects compared to controls, with NfL showing the most effective diagnostic performance. Importantly, all three biomarkers were increased compared to neurodegenerative disease controls and, specifically, to patients with Alzheimer's disease (AD; N = 44), with NfL and CHIT1 being also higher in ALS than in alpha-synucleinopathies (N = 22). Notably, ALS patients displayed increased CHIT1 levels despite having, compared to controls, a higher prevalence of a polymorphism lowering CHIT1 expression. While no relationship was found between CSF miR-181b and clinical measures in ALS (disease duration, functional disability, and disease progression rate), CSF NfL was the best independent predictor of disease progression and survival. This study deepens our knowledge of ALS biomarkers, highlighting the relative specificity of CHIT1 for ALS among neurodegenerative diseases and appraising the potential diagnostic utility of CSF miR-181b.