Summary
| Direction in Long COVID | ↑ Elevated — higher than in the comparison group |
|---|---|
| Category | Neurological |
| Also described as | Astrocyte protein |
| Compared against | HC (healthy controls) |
| Associated symptoms | Blood-brain barrier disruption |
| Test type | Blood test (serum / plasma / whole blood) |
| Source | Baalbaki et al. 2025 — doi:10.1111/all.16526 |
| Condition atlas | Long COVID Biomarker Atlas |
Other conditions where S100B is reported
- S100B in Epilepsy — ↑ elevated vs epileptic patients vs healthy controls
- S100B in Gulf War Illness — ↕ inconsistent vs HGV
See the cross-condition hub: S100B across conditions.
Related Neurological markers in Long COVID
Full list: Long COVID Biomarker Atlas.
Frequently asked questions
Is S100B high or low in Long COVID?
Elevated. Studies summarised in the OSMF atlas report higher S100B in Long COVID than in healthy controls. Source: Baalbaki et al. 2025.
What symptoms is S100B associated with in Long COVID?
The cited literature associates this marker with Blood-brain barrier disruption. These are population-level associations and do not mean the marker causes the symptoms.
Which test measures S100B?
It is measured as a blood test (serum / plasma / whole blood). Many of the cited studies used research-grade assays, so clinical availability may vary.
Is one abnormal S100B result diagnostic of Long COVID?
No. No single biomarker is diagnostic of Long COVID. S100B 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 S100B specific to Long COVID?
No. The same marker is also reported in Epilepsy, Gulf War Illness 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.