Cerebrospinal fluid (CSF) and blood-based biomarkers represent minimally invasive approaches for diagnosis, differential diagnosis, and disease monitoring in progressive supranuclear palsy (PSP). These biomarkers reflect the underlying neuropathological processes including tau pathology, neurodegeneration, and neuroinflammation.
Fluid biomarkers in PSP can be categorized into several groups:
| Category |
Source |
Key Analytes |
| Tau-related |
CSF, Blood |
Total tau, phosphorylated tau, tau fragments |
| Neurodegeneration |
CSF, Blood |
NfL, NSE, UCH-L1 |
| Neuroinflammation |
CSF, Blood |
IL-6, TNF-α, YKL-40 |
| Iron metabolism |
CSF, Blood |
Ferritin, hepcidin |
| Lipid metabolism |
CSF |
Apolipoprotein E |
Total tau reflects neuronal damage and axonal degeneration:
- Elevated levels in PSP compared to healthy controls
- Correlates with disease severity and progression
- Higher levels in PSP-RS compared to PSP-P variants
- Distinguishes PSP from Parkinson's disease
Phosphorylated tau at specific epitopes provides disease-specific information:
- p-tau181: Elevated in PSP vs. PD, but lower than AD
- p-tau217: Higher sensitivity for 4R-tauopathies like PSP
- p-tau231: Correlates with disease duration
- The 4R-tau isoforms predominate in PSP, affecting p-tau patterns
¶ Tau Fragments and Tau Oligomers
- Tau fragments: C-terminal fragments elevated in PSP CSF
- Tau oligomers: Emerging biomarker with high specificity
- Correlate with tau aggregate load in brain
NfL is a marker of axonal damage:
- Markedly elevated in PSP CSF compared to controls
- Higher than in Parkinson's disease but lower than in ALS
- Correlates with disease progression rate
- Predicts clinical deterioration
- Useful for disease monitoring in clinical trials
pNfH is a more specific marker for large-caliber myelinated axon damage:
- Elevated in PSP CSF compared to healthy controls
- Higher levels in PSP-RS vs. PSP-P variants
- Good specificity for distinguishing PSP from PD (75-85%)
- Correlates with disease severity and progression
- Complementary to NfL — using both improves diagnostic accuracy
Longitudinal trends:
- Annual increase in pNfH correlates with clinical deterioration
- Rate of change predicts progression velocity
- Combined pNfH + NfL monitoring provides comprehensive axonal health assessment
Treatment monitoring:
- pNfH serves as pharmacodynamic biomarker in PSP clinical trials
- Baseline to 6-month changes predict treatment response
- Stabilization of pNfH trajectory suggests disease modification
- Used as secondary endpoint in tau-directed therapy trials
See pNfH Biomarker for detailed information.
- Elevated in PSP CSF
- Reflects neuronal loss
- Correlates with cognitive impairment
- Elevated in PSP CSF
- Associated with neurodegeneration
- May distinguish PSP from other parkinsonian syndromes
- Elevated in PSP CSF
- Correlates with disease severity
- Reflects ongoing neuroinflammatory processes
- Increased levels in PSP CSF
- Associated with disease progression
- Therapeutic target potential
- Elevated in PSP CSF
- Marker of microglial activation
- Correlates with disease duration
- Astrocytic marker
- Elevated in PSP
- Reflects astrocytic pathology
- Elevated in PSP CSF
- Reflects iron dysregulation
- Correlates with disease severity
- Related to brain iron accumulation
- Altered iron metabolism
- Potential biomarker for PSP
¶ Lipid and Membrane Markers
- ApoE4 associated with faster progression
- Influences tau pathology
- Lipid metabolism alterations in PSP
- Altered in PSP CSF
- Related to myelin degeneration
¶ Plasma and Serum Tau
- Elevated in PSP vs. healthy controls
- Similar pattern to CSF but lower sensitivity
- Potential for screening
- p-tau181: Elevated in PSP, lower than AD
- p-tau217: Promising for 4R-tauopathies
- Can distinguish PSP from PD
- Emerging use in clinical trials
- Various tau fragments detectable in blood
- Disease-specific patterns emerging
- Reliably elevated in PSP plasma/serum
- Correlates with CSF NfL
- Excellent for disease monitoring
- Predicts progression
- Used as endpoint in clinical trials
- Elevated in PSP blood
- Less robust than CSF findings
- Research utility
- Serum ferritin elevated
- Reflects systemic iron dysregulation
- Tau enrichment in neuronal exosomes
- Specific tau strains in exosomes
- Promising for differential diagnosis
- Increased levels in PSP
- Potential for early detection
| Characteristic |
CSF |
Blood |
| Sensitivity |
Higher |
Lower |
| Specificity |
Higher |
Moderate |
| Invasiveness |
Lumipuncture |
Blood draw |
| Clinical use |
Research |
Emerging |
| Biomarker overlap |
Substantial |
Growing |
Multi-marker panels improve diagnostic accuracy:
- t-tau + NfL + IL-6: High discrimination
- p-tau217 + NfL: Progression prediction
- Tau oligomers + NfL: Disease staging
Fluid biomarkers aid in differential diagnosis:
- PSP vs. PD: NfL, t-tau elevated in PSP
- PSP vs. CBS: Different p-tau patterns
- PSP vs. AD: Lower p-tau181, different p-tau217 patterns
Serial measurements track progression:
- NfL: Annual change correlates with clinical decline
- t-tau: Progression marker
- p-tau: May plateau in later stages
Fluid biomarkers serve as:
- Enrollment criteria: Enrich for specific biomarker profiles
- Endpoint measures: NfL as progression marker
- Pharmacodynamic markers: Target engagement indicators
- Baseline NfL predicts progression rate
- p-tau patterns predict phenotype
- Multiple markers improve prognostic accuracy
- Collection: Standardized lumbar puncture protocol
- Storage: -80°C storage, avoid freeze-thaw cycles
- Timing: Morning collection preferred
- ELISA: Most common, standardized
- Simoa: Ultra-sensitive for low-abundance proteins
- Mass spectrometry: For precise tau species measurement
- Multiplex: For biomarker panels
- Laboratory-specific cutoffs
- Age-adjusted reference ranges
- Disease-specific thresholds emerging
Fluid biomarkers complement imaging:
- NfL + MRI: Progression assessment
- p-tau + Tau PET: Pathology confirmation
- Multiple markers + DTI: Network degeneration
- Ultra-sensitive assays improving detection
- Standardization across laboratories
- Point-of-care testing potential
- Tau strain-specific antibodies
- Single-molecule detection
- Multi-omic approaches
- Validation in large cohorts
- FDA/EMA approval pathways
- Integration into diagnostic criteria