Plasma pTau217 / Amyloid-β42 Ratio Test
Blood-based biomarker testing for Alzheimer’s disease is now available at Annasawmy Mudaliar General Hospital, Bengaluru, at a reduced cost, as part of our commitment to making advanced diagnostic services more accessible and affordable.
This test measures two proteins associated with Alzheimer’s disease pathology – phosphorylated tau-217 (pTau217) and amyloid-beta 1-42 (Aβ42) – and calculates their ratio to help assess the likelihood of underlying Alzheimer’s disease-related changes in individuals with cognitive impairment.
What Does the Test Measure?
Phosphorylated Tau-217 (pTau217)
pTau217 is a form of tau protein closely associated with Alzheimer’s disease pathology. Elevated levels in the blood may indicate underlying Alzheimer’s disease-related changes in the brain.
Amyloid-beta 1-42 (Aβ42)
Amyloid-beta is a protein involved in the formation of amyloid plaques, one of the characteristic features of Alzheimer’s disease. Changes in its concentration in blood may provide additional information about underlying amyloid pathology.
pTau217 / Aβ42 Ratio
The ratio combines information from both biomarkers to help estimate the likelihood of Alzheimer’s disease-associated pathology. Results are interpreted using test-specific thresholds.
Understanding the Results
The pTau217 / Aβ42 ratio helps doctors assess the likelihood of Alzheimer’s disease-related pathology in the brain.
Results can fall into three categories:
Negative: Indicates a low likelihood of Alzheimer’s disease-associated amyloid pathology, helping doctors consider other possible causes of cognitive symptoms.
Indeterminate: The result falls between the positive and negative thresholds. Additional investigations, such as amyloid PET imaging or cerebrospinal fluid testing, may help clarify the findings.
Positive: Indicates a high likelihood of Alzheimer’s disease-associated amyloid pathology, providing valuable evidence to support diagnosis and guide further clinical management.
Who Is the Test For?
Blood-based biomarker testing offers a minimally invasive approach to investigating Alzheimer’s disease pathology in individuals experiencing cognitive symptoms, such as memory difficulties, language problems, or other cognitive changes, where Alzheimer’s disease is suspected.
It may help clinicians:
- Support the differential diagnosis of cognitive impairment by assessing the likelihood of Alzheimer’s disease pathology.
- Guide decisions about further investigations, including amyloid PET imaging or cerebrospinal fluid biomarker testing.
- Inform treatment planning, including the evaluation of patients being considered for disease-modifying therapies, where additional eligibility assessments may be required.
ⓘ
This test is not intended for screening asymptomatic individuals.
Testing must be recommended by a treating doctor following clinical evaluation.
Important: Blood-based biomarker testing is only one component of a comprehensive diagnostic evaluation. Results cannot independently confirm or exclude Alzheimer’s disease and must be interpreted alongside clinical findings, cognitive assessment, and other relevant investigations.