The guide to
Physician’s Guide to Blood-Based Biomarkers for Alzheimer’s Disease
Appropriate use guidelines for blood tests
Advances in blood-based biomarkers
Interpreting blood test results
narration
What are blood-based biomarkers?
Blood-based biomarkers are proteins detected in the blood that provide a proxy measure of beta-amyloid pathology in the brain. Blood-based biomarkers are validated against cerebrospinal fluid tests, amyloid PET scans, or autopsies.
- While there are many blood tests on the market, only two are cleared by the FDA: Roche's test for ruling out Alzheimer's pathology and Fujirebio’s test for confirming pathology.
- All blood tests currently on the market have been developed and tested in older, cognitively impaired populations.
- Depending on the accuracy of the test, they may be used to triage at-risk patients for further testing or to confirm a diagnosis.
narration
Read more
Benefits of blood-based testing for Alzheimer's
Blood tests are a minimally invasive method for assessing patients with cognitive impairment, when compared to lumbar punctures or amyloid PET scans.
Less invasive
Blood draws are widely available and don’t require any specialty procedures. However, insurance coverage for blood tests is variable.
Accessible
Simulation studies suggest that blood tests might speed up Alzheimer’s diagnosis and allow people to access disease-modifying drugs sooner. However, studies have yet to assess how blood tests impact patient care in the real world.
Clinically valuable
narration
Read more
Blood-based biomarkers
Beta-amyloid plaques and tau tangles in the brain are hallmarks of Alzheimer’s disease. Fragments of beta-amyloid and tau, as well as other inflammation-related proteins, leak out from the brain and into the bloodstream. Measures of these proteins in the blood correlate with levels of beta-amyloid plaques in the brain.
Common blood-based biomarkers for Alzheimer's
Since different blood-based biomarker tests use different assays, the results of two different tests looking at the same biomarker are not comparable.
pTau-217
pTau-218
Aβ 42/40
pTau-217/npTau-217
NfL
GFAP
For more information on current tests, visit the Blood Test Performance Database.
narration
Blood-based biomarkers for Alzheimer’s
Combos
Standalone
Aß42/40 Ratio, ApoE and Age
p-Tau217
p-Tau218
pTau 217 / β-Amyloid 1-42 Ratio
p-Tau 217, Aβ42/40, NfL, and GFAP
Aß42/40
Aß42/40 Ratio and p-Tau217/np-Tau217 Ratio
Aβ 42/40, p-Tau217, and ApoE Evaluation
Aβ 42/40 and p-Tau217
narration
Blood-based biomarkers for Alzheimer’s
" p tau 217 is the best performing measure of amyloid and really tau pathology that's widely available."--Suzanne Schindler
narration
Blood-based biomarkers for Alzheimer’s
"I do not, just as a matter of principle, do biomarker testing in people who are asymptomatic [...] We don't have any improved treatments right now for people who are asymptomatic and biomarker positive, so there's not something that I could prescribe for them if they're positive."-- Suzanne Schindler
narration
Appropriate use recommendations for blood tests
Alzheimer’s Association Guidelines
The Global CEO Initiative on Alzheimer’s Disease Acceptable Performance Criteria
Testing of cognitively unimpaired individuals?
No
No
Please note
Primary care doctors or specialists
Who should administer blood tests?
Specialists
≥90% sensitivity≥85% specificity in primary care ≥75% specificity in specialty/ secondary care
Recommendations for triage setting to rule in or rule out Alzheimer’s
≥90% sensitivity≥75% specificity
≥90% sensitivity≥90% specificity
Recommendations for confirmatory blood tests
≥90% sensitivity≥90% specificity
narration
Understanding how well a blood test works
Sensitivity: How often a test detects a true positive.Specificity: How often a test correctly detects a negative result. Positive Predictive Value (PPV): The chances that someone who tests positive actually has the condition or disease that’s being tested for.
PPV% = True Positives / (True Positives + False Positives) * 100
When a population of cognitively healthy adults is tested, the positive predictive value declines since it introduces more false positive results.
narration
Interpreting blood test results
Confirmatory tests
Triage tests
narration
Do tests need FDA clearance?
Most blood tests on the market are laboratory-developed tests (LDTs). LDTs are regulated to ensure they pass quality benchmarks, but do not require proof of effectiveness.
As of May 2024, any new blood tests heading to market will require FDA clearance, however tests that were already available on the market would be exempt. Roche's Eclysys pTau181 test is the only one cleared by the FDA for ruling out Alzheimer's as a potential cause of cognitive decline in a primary care setting. Fujirebio’s Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio test is the only one cleared by the FDA for use in confirming diagnosis; its results are equivalent to other forms of biomarker testing.
narration
Counselling after the blood test
1. Call patients and explain the results to them. Key considerations:
- The blood test alone doesn't provide a definitive diagnosis.
- High-risk patients with two copies of ApoE4 who test negative may test positive in the future.
- Depending on the test, there may be a small risk of false positives or false negatives.
2. Discuss next steps for further biomarker or cognitive testing:
- Additional testing for high risk patients with indeterminate result.
- Discuss future screenings for older patients.
- Track biomarkers along with cognitive baseline.
3. If the confirmatory test is positive, discuss potential lifestyle changes, available mABs, and clinical trial enrollment
narration
Counselling after the blood test
""I would say that negative biomarker results are the most distressing to patients. That's not what you might expect, but these are patients who have cognitive impairment and they're worried they have Alzheimer's disease [...] I have to go through again and say, No, your cognitive impairment is real, and I absolutely understand all the issues that you're having that they're very significant. It's just that the cognitive impairment is not due to Alzheimer's disease"-- Suzanne Schindler
narration
The future of blood tests
Blood-based biomarkers are evolving.
- Finger-prick tests are being developed that make measurement easier.
- Large studies are testing whether any blood-based biomarkers could predict Alzheimer’s in healthy individuals.
- Blood tests are being tested to see if they can help track the efficacy of anti-amyloid drugs.
- Blood tests are being combined with AI-powered cognitive screening tools to better assess risk.
- Blood tests are being used to understand whether lifestyle interventions affect beta-amyloid and tau in the brain.
- New biomarkers like MTBR-tau are being developed to improve test accuracy.
narration
Want to learn more?
Visit
beingpatient.com
for the latest news and information on brain health and dementia
narration
Triage tests
- A positive result indicates that a patient might have beta-amyloid pathology and should receive further testing.
- A negative result rules out Alzheimer’s disease and suggests the patient’s cognitive impairment has another cause.
Purpose
To confirm the presence or absence of Alzheimer's pathology after a doctor has done other tests
Negative result
Positive result
- Low likelihood of Alzheimer's- Regular monitoring advised
- Further evaluation needed- Additional diagnostic tests
Intermediate result
- Repeat testing in the future- Possible interfering factors
Confirmatory tests
- A positive result indicates that a patient might have beta-amyloid pathology. Combined with a clinical assessment, this test result can confirm an Alzheimer’s diagnosis.
- An indeterminate result means that more testing is needed to get a definitive answer.
- A negative result suggests that the patient does not have significant levels of beta-amyloid plaques in the brain and that their cognitive impairment has another cause.
Purpose
To help clinicians understand whether Alzheimer's is a possibility at the start of a diagnosis process for people showing cognitive symptoms.
Negative result
Positive result
Initial test shows no concerning levels of biomarkers - No immediate concerns identified - Continue routine health monitoring
Initial test indicates potential presence of biomarkers- Referral to specialist recommended - Additional confirmation testing needed - Does not confirm diagnosis
Physician's Guide BBM
Deborah Kan
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Transcript
The guide to
Physician’s Guide to Blood-Based Biomarkers for Alzheimer’s Disease
Appropriate use guidelines for blood tests
Advances in blood-based biomarkers
Interpreting blood test results
narration
What are blood-based biomarkers?
Blood-based biomarkers are proteins detected in the blood that provide a proxy measure of beta-amyloid pathology in the brain. Blood-based biomarkers are validated against cerebrospinal fluid tests, amyloid PET scans, or autopsies.
narration
Read more
Benefits of blood-based testing for Alzheimer's
Blood tests are a minimally invasive method for assessing patients with cognitive impairment, when compared to lumbar punctures or amyloid PET scans.
Less invasive
Blood draws are widely available and don’t require any specialty procedures. However, insurance coverage for blood tests is variable.
Accessible
Simulation studies suggest that blood tests might speed up Alzheimer’s diagnosis and allow people to access disease-modifying drugs sooner. However, studies have yet to assess how blood tests impact patient care in the real world.
Clinically valuable
narration
Read more
Blood-based biomarkers
Beta-amyloid plaques and tau tangles in the brain are hallmarks of Alzheimer’s disease. Fragments of beta-amyloid and tau, as well as other inflammation-related proteins, leak out from the brain and into the bloodstream. Measures of these proteins in the blood correlate with levels of beta-amyloid plaques in the brain.
Common blood-based biomarkers for Alzheimer's
Since different blood-based biomarker tests use different assays, the results of two different tests looking at the same biomarker are not comparable.
pTau-217
pTau-218
Aβ 42/40
pTau-217/npTau-217
NfL
GFAP
For more information on current tests, visit the Blood Test Performance Database.
narration
Blood-based biomarkers for Alzheimer’s
Combos
Standalone
Aß42/40 Ratio, ApoE and Age
p-Tau217
p-Tau218
pTau 217 / β-Amyloid 1-42 Ratio
p-Tau 217, Aβ42/40, NfL, and GFAP
Aß42/40
Aß42/40 Ratio and p-Tau217/np-Tau217 Ratio
Aβ 42/40, p-Tau217, and ApoE Evaluation
Aβ 42/40 and p-Tau217
narration
Blood-based biomarkers for Alzheimer’s
" p tau 217 is the best performing measure of amyloid and really tau pathology that's widely available."--Suzanne Schindler
narration
Blood-based biomarkers for Alzheimer’s
"I do not, just as a matter of principle, do biomarker testing in people who are asymptomatic [...] We don't have any improved treatments right now for people who are asymptomatic and biomarker positive, so there's not something that I could prescribe for them if they're positive."-- Suzanne Schindler
narration
Appropriate use recommendations for blood tests
Alzheimer’s Association Guidelines
The Global CEO Initiative on Alzheimer’s Disease Acceptable Performance Criteria
Testing of cognitively unimpaired individuals?
No
No
Please note
Primary care doctors or specialists
Who should administer blood tests?
Specialists
≥90% sensitivity≥85% specificity in primary care ≥75% specificity in specialty/ secondary care
Recommendations for triage setting to rule in or rule out Alzheimer’s
≥90% sensitivity≥75% specificity
≥90% sensitivity≥90% specificity
Recommendations for confirmatory blood tests
≥90% sensitivity≥90% specificity
narration
Understanding how well a blood test works
Sensitivity: How often a test detects a true positive.Specificity: How often a test correctly detects a negative result. Positive Predictive Value (PPV): The chances that someone who tests positive actually has the condition or disease that’s being tested for.
PPV% = True Positives / (True Positives + False Positives) * 100
When a population of cognitively healthy adults is tested, the positive predictive value declines since it introduces more false positive results.
narration
Interpreting blood test results
Confirmatory tests
Triage tests
narration
Do tests need FDA clearance?
Most blood tests on the market are laboratory-developed tests (LDTs). LDTs are regulated to ensure they pass quality benchmarks, but do not require proof of effectiveness.
As of May 2024, any new blood tests heading to market will require FDA clearance, however tests that were already available on the market would be exempt. Roche's Eclysys pTau181 test is the only one cleared by the FDA for ruling out Alzheimer's as a potential cause of cognitive decline in a primary care setting. Fujirebio’s Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio test is the only one cleared by the FDA for use in confirming diagnosis; its results are equivalent to other forms of biomarker testing.
narration
Counselling after the blood test
1. Call patients and explain the results to them. Key considerations:
- The blood test alone doesn't provide a definitive diagnosis.
- High-risk patients with two copies of ApoE4 who test negative may test positive in the future.
- Depending on the test, there may be a small risk of false positives or false negatives.
2. Discuss next steps for further biomarker or cognitive testing:- Additional testing for high risk patients with indeterminate result.
- Discuss future screenings for older patients.
- Track biomarkers along with cognitive baseline.
3. If the confirmatory test is positive, discuss potential lifestyle changes, available mABs, and clinical trial enrollmentnarration
Counselling after the blood test
""I would say that negative biomarker results are the most distressing to patients. That's not what you might expect, but these are patients who have cognitive impairment and they're worried they have Alzheimer's disease [...] I have to go through again and say, No, your cognitive impairment is real, and I absolutely understand all the issues that you're having that they're very significant. It's just that the cognitive impairment is not due to Alzheimer's disease"-- Suzanne Schindler
narration
The future of blood tests
Blood-based biomarkers are evolving.
narration
Want to learn more?
Visit
beingpatient.com
for the latest news and information on brain health and dementia
narration
Triage tests
Purpose
To confirm the presence or absence of Alzheimer's pathology after a doctor has done other tests
Negative result
Positive result
- Low likelihood of Alzheimer's- Regular monitoring advised
- Further evaluation needed- Additional diagnostic tests
Intermediate result
- Repeat testing in the future- Possible interfering factors
Confirmatory tests
Purpose
To help clinicians understand whether Alzheimer's is a possibility at the start of a diagnosis process for people showing cognitive symptoms.
Negative result
Positive result
Initial test shows no concerning levels of biomarkers - No immediate concerns identified - Continue routine health monitoring
Initial test indicates potential presence of biomarkers- Referral to specialist recommended - Additional confirmation testing needed - Does not confirm diagnosis