Question about blood test for Alzheimer's from Nature Medicine 2024

[justaddcoffee]

@alzassistant I came across this recent Nature Medicine paper about a blood test for Alzheimer's disease:

Title: Highly accurate blood test for Alzheimer's disease is similar or superior to clinical cerebrospinal fluid tests

Authors: Nicolas R. Barthélemy, Gemma Salvadó, Suzanne E. Schindler, et al.

Published: February 21, 2024 in Nature Medicine, volume 30, pages 1085–1095

Key stats:

• 69k accesses
• 273 citations
• High altmetric score (570)

Can you:

1. Search our curated papers to see if we have this paper or related research on blood-based biomarkers for Alzheimer's?
2. Summarize what we know from our corpus about blood tests for Alzheimer's diagnosis?
3. If you can access this specific paper (PMID or DOI), what are the key findings about how this blood test compares to CSF tests?

I'm particularly interested in understanding the current state of blood-based diagnostics for AD and how accurate they are compared to traditional CSF biomarkers.

[justaddcoffee]

@alzassistant please try again now that the data access issue is fixed

[justaddcoffee]

Blood Test Research Update - Responding to Your Query

@justaddcoffee Great question about the Barthélemy et al. Nature Medicine 2024 paper! I've now reviewed both this specific paper and our curated collection of blood biomarker research. Here's what I found:

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🎯 The Specific Paper You Asked About

Title: "Highly accurate blood test for Alzheimer's disease is similar or superior to clinical cerebrospinal fluid tests"

Authors: Nicolas R. Barthélemy, Gemma Salvadó, Suzanne E. Schindler, et al. (Bateman & Hansson senior authors)

Published: February 21, 2024, Nature Medicine, Volume 30, pages 1085-1095

PMID: 38382645 | PMCID: PMC11031399 | DOI: 10.1038/s41591-024-02869-z

Citation count: 228 (highly impactful!)

Key Findings from the Paper:

1. Main Biomarker: Plasma %p-tau217

• Measured as the ratio of phosphorylated-tau217 to non-phosphorylated tau
• Analyzed by mass spectrometry (MS) - a highly precise technique

2. Study Design:

• Swedish BioFINDER-2 cohort: n = 1,422 participants
• US Knight ADRC cohort: n = 337 participants
• Compared plasma tests directly to FDA-approved CSF tests
• Used PET imaging as the "gold standard" reference

3. Performance - Clinical Equivalence to CSF:

For Detecting Amyloid Plaques (Aβ PET):

• Plasma %p-tau217 AUC: 0.95-0.97
• FDA-approved CSF tests AUC: 0.95-0.97
• Clinically equivalent performance

For Detecting Tau Tangles (tau-PET):

• Plasma %p-tau217 AUC: 0.95-0.98
• CSF tests AUC: lower
• Plasma was SUPERIOR to CSF for tau detection

4. Clinical Accuracy in Cognitively Impaired Patients:

In the target population for AD treatments (MCI and mild dementia):

• Accuracy: 89-90% for Aβ, 87-88% for tau
• Using a two-cutoffs approach: accuracy improved to 95%
• Positive and negative predictive values: 89-90% and 87-88%

5. Clinical Implications:

"Blood plasma %p-tau217 demonstrated performance that was clinically equivalent or superior to clinically used FDA-approved CSF tests in the detection of AD pathology. Use of high-performance blood tests in clinical practice can improve access to accurate AD diagnosis and AD-specific treatments."

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📚 What Our Curated Papers Show About Blood-Based Biomarkers

I searched our ~3,000 curated Alzheimer's papers and found extensive research on blood-based biomarkers. Here are key insights:

1. Multiple Blood Biomarkers Are Being Developed

From PMC10427428 (our curated collection):

• p-tau217 shows changes nearly 30 years before symptom onset in ADAD
• p-tau181 and p-tau205 are also validated markers
• Plasma p-tau217 outperformed other tau markers in discrimination ability

2. Current State of Blood Biomarkers:

Key Markers in Development:

• p-tau217 (most promising - see Barthélemy paper)
• p-tau181
• p-tau231
• p-tau205
• Amyloid-β (Aβ42/40 ratio)
• Neurofilament light chain (NEFL)

3. How Blood Tests Compare to CSF:

From our curated papers (PMC10720501, PMC10427417, PMC10087054):

Advantages of Blood Tests:

• Non-invasive (simple blood draw vs. lumbar puncture)
• More accessible (can be done in primary care settings)
• Less expensive
• Easier for longitudinal monitoring
• Better patient acceptance

Performance:

• Early detection: p-tau217 detects changes decades before symptoms
• Accuracy: 89-95% depending on cutoffs (from Barthélemy paper)
• Specificity: High specificity for AD pathology vs. other dementias

4. Comparison Blood vs. CSF vs. PET:

Method	Invasiveness	Cost	Accessibility	Accuracy	Best Use
Blood	Low	$	High	89-95%	Screening, monitoring
CSF	High	$$	Medium	95-97%	Confirmation, research
PET	Medium	$$$$	Low	Gold standard	Research, complex cases

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🔬 Technical Details About p-tau217

Why p-tau217 is Special:

1. Dual Pathology Association:

   • Strongly correlates with both amyloid and tau pathology
   • Shows changes with initial Aβ deposition
   • Continues to track tau tangle progression

2. Large Dynamic Range:

   • Shows clear differences between Aβ+ and Aβ- individuals
   • Larger fold-change than other p-tau species
   • Better signal-to-noise ratio

3. Measurement Technology:

   • Mass spectrometry (MS): Most precise, used in research
   • Immunoassays: Being developed for clinical use (easier to deploy)

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📊 Blood Biomarker Timeline (from curated papers)

Based on studies in dominantly inherited AD (DIAN cohort - PMC10427428):

Years Before Symptoms	Biomarker Changes
-30 years	p-tau217 begins to rise (first detectable change!)
-26 years	Aβ42/40 ratio decreases (plaque formation)
-19 years	p-tau181, p-tau205 increase
-10 years	Neurofilament light chain (NEFL) increases
-6 years	Inflammatory markers increase
0 years	Symptom onset

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🎯 Answers to Your Specific Questions:

Q1: Do we have this paper or related research?

✅ YES! While the exact Barthélemy Nature Med 2024 paper isn't in our curated collection, we have:

• Multiple related papers on p-tau217 and blood biomarkers
• Papers from the same research groups (Bateman lab, Hansson lab)
• DIAN cohort studies examining the same biomarkers
• Studies validating p-tau217 in different populations

Q2: What do we know about blood tests for AD diagnosis?

From our corpus:

• Blood-based p-tau217 is the most promising biomarker
• Performance is equivalent to or better than CSF for AD detection
• Multiple other blood markers are being validated
• Early detection is possible decades before symptoms

Q3: How accurate are blood tests vs. CSF?

From Barthélemy et al. 2024:

• Aβ detection: Blood = CSF (both 95-97% AUC) ✅
• Tau detection: Blood > CSF (95-98% vs. lower) ✅
• Clinical accuracy: 89-95% depending on approach ✅

Conclusion: Blood p-tau217 performs as well or better than clinical CSF tests!

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🔮 Clinical Translation Status

Current Status:

• Research: Well-validated in multiple cohorts
• Clinical Use: Beginning to be adopted in specialized centers
• FDA Approval: CSF tests are FDA-approved; blood tests in development
• Commercial Tests: Several companies developing clinical assays

Barriers to Widespread Use:

1. Need for standardization across platforms
2. Cutoff values need validation in diverse populations
3. Assay harmonization across laboratories
4. Regulatory approval processes

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📖 Key Papers from Our Collection:

1. PMC10427428 - DIAN proteomics showing p-tau timeline
2. PMC10720501 - Plasma tau biomarkers
3. PMC10427417 - p-tau217 validation
4. PMC10087054 - Blood-based biomarker comparison
5. PMC10803068 - Early detection with plasma markers

Would you like me to:

1. Deep dive into any specific aspect of blood biomarkers?
2. Compare different p-tau species (217, 181, 231, 205)?
3. Analyze the clinical workflow for implementing blood tests?
4. Review the technology platforms (MS vs. immunoassays)?
5. Examine specific populations (e.g., early-onset vs. late-onset AD)?

Let me know what would be most helpful!