Memory & Dementia
Signs of Dementia: When Memory Changes May Be More Than Normal Aging
Amarish Dave, DO, Board-Certified Neurologist, explains important signs that memory or thinking changes may be more than normal aging.
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New Alzheimer's Blood Tests: Who Should Get Them?
Amarish Dave, DO, Board-Certified Neurologist, explains how newer Alzheimer's blood biomarkers are changing the evaluation of memory loss—and who should get tested.
Written and medically reviewed by Amarish Dave, DO, board-certified neurologist. This page is educational and does not replace an individual medical evaluation.
Newer Alzheimer's blood tests are changing how memory loss and suspected Alzheimer's disease are evaluated. Instead of relying only on symptoms, clinicians can now measure blood biomarkers such as p-tau217 and the beta-amyloid 42/40 ratio that reflect the biological changes associated with Alzheimer's disease. These are not standalone answers—a new blood test for Alzheimer's is one part of a complete neurological evaluation, which also includes the history, cognitive testing, examination, and other appropriate testing.
Who Should Get an Alzheimer's Blood Test?
These tests are most useful in people who have cognitive symptoms or objective evidence of cognitive impairment when Alzheimer's disease is being considered. Examples include:
- Progressive memory loss
- Repeating questions or conversations
- Difficulty managing medications or finances
- Increasing problems with planning or problem-solving
- Word-finding or other cognitive changes
- Mild cognitive impairment
- Cognitive symptoms beginning to interfere with everyday activities
It is important to emphasize that an Alzheimer's blood test should be interpreted as part of a complete neurological evaluation, not by itself. The result adds information; it does not replace clinical judgment.
Who Should NOT Get One?
These tests generally should not be treated as routine screening tests for healthy, asymptomatic adults. Someone without cognitive symptoms should not assume that getting an Alzheimer's biomarker panel is equivalent to getting routine cholesterol or diabetes screening. Testing is most meaningful when there are symptoms to explain, and results in people without symptoms can be difficult to interpret.
What Is p-Tau217?
Phosphorylated tau 217 (p-tau217) is one of the most promising blood biomarkers for detecting biological changes associated with Alzheimer's disease. The p-tau217 blood test measures this phosphorylated form of the tau protein, which tends to change as Alzheimer-type pathology develops. It is a useful piece of information—but the test does not replace clinical judgment, and results are always considered alongside symptoms and examination findings.
What Is the Beta-Amyloid 42/40 Ratio?
The beta-amyloid 42/40 ratio compares two forms of the beta-amyloid protein in blood. Changes in the relative amounts of Aβ42 and Aβ40 can provide information about amyloid pathology in the brain. Because different biomarkers reflect different parts of the disease process, combining biomarkers may improve the ability to estimate whether Alzheimer-type pathology is present.
APOE4 Is NOT the Same as an Alzheimer's Blood Biomarker
APOE4 is NOT the same thing as an Alzheimer's blood biomarker. APOE4 is a genetic risk factor. Having APOE4 does not mean someone has Alzheimer's disease or will inevitably develop it.
APOE testing can also have implications beyond the immediate memory evaluation and should be ordered thoughtfully. APOE status may become clinically relevant when evaluating certain patients for anti-amyloid treatments, because APOE4 can influence the risk of ARIA (amyloid-related imaging abnormalities) that can occur with those therapies.
A Positive Blood Test Does Not Automatically Mean Dementia
Alzheimer's pathology and dementia are not the same thing. A positive or abnormal blood test for dementia does not by itself establish a diagnosis. Blood biomarkers must be interpreted alongside the patient's symptoms, neurological examination, cognitive testing, medical history, imaging, and other appropriate testing.
When Should You See a Neurologist?
An evaluation is worth considering when there are persistent or progressive changes in:
- Memory
- Language
- Judgment
- Navigation
- Personality or behavior
- Ability to manage everyday activities
You can learn more in our overviews of memory loss, mild cognitive impairment, and Alzheimer's disease, and in our dementia evaluation guide. To see how this testing fits into treatment, read about the new Alzheimer's disease treatment, including Leqembi and Kisunla, and watch the signs of dementia.
Frequently asked questions
- Who should get an Alzheimer's blood test?
- Alzheimer's blood tests are most useful in people who have cognitive symptoms or objective evidence of cognitive impairment—such as progressive memory loss, repeating questions, difficulty managing medications or finances, or mild cognitive impairment—when Alzheimer's disease is being considered. They are not routine screening tests for healthy, asymptomatic adults.
- What is p-tau217?
- Phosphorylated tau 217 (p-tau217) is one of the most promising blood biomarkers for detecting biological changes associated with Alzheimer's disease. It is best interpreted as part of a complete neurological evaluation, not on its own.
- What is the beta-amyloid 42/40 ratio?
- It is a blood measurement comparing two forms of beta-amyloid protein. Changes in the relative amounts of Aβ42 and Aβ40 can provide information about amyloid pathology in the brain, and combining biomarkers can improve the ability to estimate whether Alzheimer-type pathology is present.
- Is APOE4 the same as an Alzheimer's blood test?
- No. APOE4 is a genetic risk factor, not a biomarker that measures Alzheimer's pathology. Having APOE4 does not mean someone has Alzheimer's disease or will inevitably develop it. APOE testing has implications beyond a memory evaluation and should be ordered thoughtfully.
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Concerned about memory loss or Alzheimer's disease?
NeurologistCare provides neurological evaluation for memory loss, mild cognitive impairment, Alzheimer's disease, and other causes of cognitive change. In-person appointments are available in Crystal Lake and Woodstock, Illinois, and Lake Geneva, Wisconsin, with televisits available for appropriate patients in Illinois and Wisconsin.
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