Blood NfL A biomarker for disease severity and progression in Parkinson disease

Objective To examine whether plasma neurofilament light chain (NfL) levels were associated with motor and cognitive progression in Parkinson disease (PD). Methods This prospective follow-up study enrolled 178 participants, including 116 with PD, 22 with multiple system atrophy (MSA), and 40 healthy controls. We measured plasma NfL levels with electrochemiluminescence immunoassay. Patients with PD received evaluations of motor and cognition at baseline and at a mean follow-up interval of 3 years. Changes in the Unified Parkinson's Disease Rating Scale (UPDRS) part III motor score and Mini-Mental State Examination score were used to assess motor and cognition progression. Results Plasma NfL levels were significantly higher in the MSA group than in the PD and healthy groups (35.8 +/- 6.2, 17.6 +/- 2.8, and 10.6 +/- 2.3 pg/mL, respectively, p < 0.001). In the PD group, NfL levels were significantly elevated in patients with advanced Hoehn-Yahr stage and patients with dementia (p < 0.001). NfL levels were modestly correlated with UPDRS part III scores (r = 0.42, 95% confidence interval 0.46-0.56, p < 0.001). After a mean follow-up of 3.4 +/- 1.2 years, a Cox regression analysis adjusted for age, sex, disease duration, and baseline motor or cognitive status showed that higher baseline NfL levels were associated with higher risks for either motor or cognition progression (p = 0.029 and p = 0.015, respectively). Conclusions Plasma NfL levels correlated with disease severity and progression in terms of both motor and cognitive functions in PD. Classification of evidence This study provides Class III evidence that plasma NfL level distinguishes PD from MSA and is a surrogate biomarker for PD progression.