Plasma biomarker testing

Alzheimer’s disease remains a challenge to diagnose, however, heightened understanding of the role of blood biomarkers has enabled the development of noninvasive blood tests that provide a diagnostic tool to aid in the evaluation of patients presenting with mild cognitive impairment or early dementia. Our plasma-based assay evaluates for phosphorylated Tau 217 (p-Tau217), which provides the highest diagnostic accuracy and specificity for the detection of amyloid pathology.  

Key testing

• PT217 | Phospho-Tau(217), Plasma

Advantages

• Noninvasive blood test with a rapid time to result (1–5 days).
• Assesses pathological accumulation of beta amyloid in the brain by measuring the amount of phosphorylated Tau 217 (p-Tau217) in plasma.
• Provides high diagnostic accuracy for the detection of brain amyloid pathology as assessed by amyloid PET imaging.
• Test interpretation cutpoints have been optimized to obtain an overall 92% sensitivity and 96% specificity for the detection of abnormal amyloid pathology based on amyloid-PET positivity.
• Uses a two-cutpoint model of result interpretation, which maximizes the overall testing accuracy.
  • A positive result is consistent with the presence of amyloid pathology and supports an Alzheimer’s disease diagnosis; a negative result indicates a reduced likelihood that an individual has neuropathological changes associated with Alzheimer’s disease; and an intermediate result cannot accurately differentiate between the presence or absence of neuropathological changes associated with Alzheimer’s disease.
  • In the case of an intermediate result, additional testing, such as amyloid PET or CSF pTau181/Aβ42 or CSF Aβ42/Aβ40 ratio, is recommended.
• Promotes increased access to dementia evaluation and potential treatment.
• Recommended for patients age 50 and older who present with symptoms of mild cognitive impairment or early dementia.
• This test is NOT intended for asymptomatic patients.
• Note: Patients with advanced chronic kidney disease may have elevated levels of p-Tau217. In these instances, careful evaluation of a positive result is required.

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Cerebrospinal fluid biomarker testing

The results from our CSF evaluations are based on ratios of p-Tau and AB42 (Mayo ID: ADEVL) and AB42 and AB40 (Mayo ID: AMYR), which allow for greater than 90% diagnostic accuracy compared to standard assessments. We also use low-binding tubes, resulting in fewer falsely abnormal results for patients.

Key testing

• ADEVL | Alzheimer Disease Evaluation, Spinal Fluid
• AMYR | Beta-Amyloid Ratio, (1-42/1-40), Spinal Fluid*
  • *Note: Only order in patients 55 years and older.

Advantages

• Uses the most up-to-date methodology (automated immunoassay).
• Evaluates multiple biomarkers and ratios.
• Aligns with consensus research diagnostic criteria for Alzheimer’s disease, mild cognitive impairment (MCI), and pre-clinical Alzheimer’s disease as proposed by the National Institute on Aging and Alzheimer’s Associate Research Framework.²
• AMYR is an FDA-approved evaluation.
• Positive result enables access to FDA-approved medications.

When to consider testing

• For the differential diagnosis of Alzheimer’s disease versus other causes of cognitive impairment.
• When patients present with atypical dementia symptoms.
• To assess Alzheimer’s disease pathology in a mixed diagnosis.
• To allow for eligibility into clinical trials.

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References

1. Alzheimer’s Disease Facts and Figures. Alzheimer’s Association. https://www.alz.org/alzheimers-dementia/facts-figures. Published 2023. Accessed Sept. 15, 2023.
2. Jack CR Jr, Bennett DA, Blennow K, et al. NIA-AA Research Framework: Toward a biological definition of Alzheimer's disease. Alzheimers Dement. 2018 Apr;14(4):535-562. doi:10.1016/j.jalz.2018.02.018. PMID: 29653606; PMCID: PMC5958625.
3. Rabinovici GD, Gatsonis C, Apgar C, et al. Association of amyloid positron emission tomography with subsequent change in clinical management among medicare beneficiaries with mild cognitive impairment or dementia. JAMA. 2019 Apr 2;321(13):1286-1294.