What does the Neurofilament Light Chain test measure?

Why is Neurofilament Light Chain measured?

Plasma NfL has emerged as a fluid biomarker of active neuroaxonal injury. It is non-specific — elevated in multiple sclerosis, Alzheimer disease, frontotemporal dementia, Parkinson disease, traumatic brain injury, and cerebrovascular disease — but this breadth makes it a sensitive screening and monitoring tool. In multiple sclerosis it correlates with relapse activity, MRI lesion burden, and treatment response; in neurodegenerative disease it tracks disease stage and progression rate. Practitioners use NfL to detect subclinical disease activity, guide escalation of disease-modifying therapy, and monitor intervention efficacy, interpreted always within the clinical and imaging context.

Reference ranges

Standard reference

Age-dependent; typically <20 pg/mL in younger adults, rising with age. Laboratory-specific intervals apply.

Functional medicine optimal

Because NfL rises with normal ageing, 'optimal' is better framed as stability over time or values within the age-stratified reference interval. Longitudinal trending is more informative than a single cross-sectional value.

Units

pg/mL, ng/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.