Summary
| Direction in Long COVID | ↑ Elevated — higher than in the comparison group |
|---|---|
| Category | Neurological |
| Also described as | Axonal damage marker |
| Compared against | HC (healthy controls) |
| Associated symptoms | Neurological LC, brain fog |
| Test type | Blood test (serum / plasma / whole blood) |
| LOINC code | 94635-5 |
| Source | Lai et al. 2023 — doi:10.3389/fmed.2023.1085988 |
| Condition atlas | Long COVID Biomarker Atlas |
Other conditions where Neurofilament light chain (NfL) is reported
- Neurofilament Light Chain (NfL) in Alzheimer's Disease and Other Dementias — ↑ elevated vs AD vs healthy/non-AD (core CSF biomarker)
- Neurofilament light chain (NfL) in ME/CFS — ↕ inconsistent vs HC
- Neurofilament Light Chain (NfL) in Multiple Sclerosis — ↑ elevated vs MS relapse/disease activity vs healthy
- Neurofilament light chain (NfL) in PACVS — ↑ elevated vs HC
See the cross-condition hub: Neurofilament light chain (NfL) across conditions.
Trials, interventions and tests
Commercial test availability
Neurofilament light chain (NfL) — specialty laboratory test. Growing specialty/neurology send-out; check local lab menus.
Links are for reference only; availability, specimen requirements and coverage vary by location.
Related Neurological markers in Long COVID
- GFAP ↑
- Tau protein ↑
- S100B ↑
Full list: Long COVID Biomarker Atlas.
Frequently asked questions
Is Neurofilament light chain (NfL) high or low in Long COVID?
Elevated. Studies summarised in the OSMF atlas report higher Neurofilament light chain (NfL) in Long COVID than in healthy controls. Source: Lai et al. 2023.
What symptoms is Neurofilament light chain (NfL) associated with in Long COVID?
The cited literature associates this marker with Neurological LC, brain fog. These are population-level associations and do not mean the marker causes the symptoms.
Which test measures Neurofilament light chain (NfL)?
It is measured as a blood test (serum / plasma / whole blood). The standard laboratory code is LOINC 94635-5. Commercial laboratories such as Quest Diagnostics, LabCorp list an orderable assay.
Is one abnormal Neurofilament light chain (NfL) result diagnostic of Long COVID?
No. No single biomarker is diagnostic of Long COVID. Neurofilament light chain (NfL) findings come from group comparisons, overlap considerably between patients and controls, and vary with study design, timing and comparison group. A result should be interpreted by a clinician alongside symptoms, history and other tests.
Is Neurofilament light chain (NfL) specific to Long COVID?
No. The same marker is also reported in Alzheimer's Disease and Other Dementias, ME/CFS, Multiple Sclerosis, PACVS in this atlas, so it reflects shared biology (for example inflammation or vascular stress) rather than a condition-specific signature.
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Last reviewed: 2026-06-29 · Page generated from long-covid.json · Browse: Long COVID atlas · Biomarker Index · All marker pages
Disclaimer: This page is an educational synthesis of published, peer-reviewed research and is not medical advice. Biomarker findings vary across studies with case definitions, comparison groups, timing and assay methods. Direction of change reflects the predominant finding in the cited source and does not establish a diagnostic threshold. Discuss any test result with a qualified clinician.