How is Alzheimer’s Diagnosed: Tests for Alzheimer’s Dementia

If there is no single test that can recognize Alzheimer’s, how is Alzheimer’s diagnosed? Is there a way to self-assess memory? Can the peanut butter test help diagnose it?

Why is Alzheimer’s disease so difficult to diagnose? How is Alzheimer’s diagnosed and how reliable are the different tests? Which specialist can give you the answers you seek?

In this article we’ll also share the myths and realities of at-home tests like the SAGE test, camel test, and the peanut butter test. Also, can the MindCrowd test diagnose dementia?

How Does a Doctor Diagnose Dementia?

The short answer to how Alzheimer’s disease is diagnosed in a living patient is through a series of memory and thinking tests that are administered face to face in the doctor’s office, brain scans, and biomarker tests.

It’s important to mention that in a living patient the Alzheimer’s disease diagnosis is not 100% accurate. Depending on the tests performed, the accuracy can range from 80 to 95 percent in a living person. The only way to be sure that an individual has Alzheimer’s disease is to look at their brain following death.

Accurate mental status testing to rule out other conditions is key. There are people who have been diagnosed with Alzheimer’s disease but they have a different medical condition that may mimic it. There are also people who have been diagnosed with other conditions who actually have Alzheimer’s dementia.

We will cover the whole process from how to assess memory loss to how to get a dementia diagnosis with the highest level of accuracy possible in a living person.

Table of Contents

How is Alzheimer's diagnosed? Is there a way to self-assess memory? Alzheimer's Myth vs fact by Dr. Matt Huentelman, Ph.D.
How is Alzheimer’s disease diagnosed? Is there a way to self-assess memory? Alzheimer’s myths vs facts by Dr. Matt Huentelman, Ph.D.

Memory and Thinking Tests to Identify Alzheimer’s Disease

In a person who is living a doctor diagnoses Alzheimer’s disease by administering a series of tests of memory and thinking performance. These tests are given one-on-one by a professionally qualified investigator.

The goal is to administer the test in the same exact way any person across the country would receive it. And then the scores of these tests are compared to what are called norms.

Norms are people who are about the same age, the same sex, the same background. So the results are compared to those scores to tell if the person is truly having memory and thinking problems.

These tests will be between 80 to 90 percent accurate. And a second opinion won’t necessarily improve the chances of getting the correct diagnosis if they simply repeat the standard memory and thinking tests.

But, depending on where you are located, other tests may be available in addition to the learning and memory tests. Let’s talk about these tests.

Diagnosing Alzheimer’s: Biomarker Tests

These are tests that look at what we call biomarkers. Biomarkers are biological chemicals or changes that are known to indicate disease. In this case we look for biomarkers of Alzheimer’s disease.

There are two main biomarker tests: the positron emission tomography or PET scan and the body fluids test (either via blood samples or spinal taps).

The Brain Scan: Does Alzheimer’s Show up on an MRI?

Brain scans or brain imaging are typically done with special agents. These special chemicals are injected into the bloodstream, travel to the brain and light up the beta amyloid plaques.

This type of imaging is called PET imaging or PET scan. It’s very specific to Alzheimer’s disease plaque pathology because of the slightly radioactive agents that are injected. Once the agents reach the brain, the patient slides into a brain scanner where the amount of Alzheimer’s plaque you have in your brain can be seen and measured.

Tests designed to light up tau tangles, the other hallmark of Alzheimer’s disease, are in development.

PET scans are good but also not 100% accurate, With a memory test alone we might be 80% to 90% accurate. A PET scan will increase the accuracy level,

After that, many physicians, if they have access to the technology, will order a secondary biomarker test. And with the additional biomarker test the accuracy can improve further.

Diagnosing Alzheimer’s: magnetic resonance imaging MRI or biomarker tests. PET imaging or PET scan to detect Alzheimer's plaque pathologies.
Diagnosing Alzheimer’s: biomarker tests. PET imaging or PET scan to detect Alzheimer’s plaque pathologies.

Is Alzheimer’s Diagnosed with a Blood Test?

The other biomarker test, uses either a blood sample or, more commonly, a cerebral spinal fluid (CSF) sample. The CSF sample is obtained via a spinal tap.

We look for markers of Alzheimer’s disease in the blood and the spinal fluid samples. These are pieces of the plaques and tangles that might be circulating in the blood or spinal fluid.

Therefore, the patient can have a thinking and memory test, and then typically the physician will add on additional tests. One could be a PET scan of the brain and the other one could be a test of either the blood or cerebral spinal fluid.

Diagnosing Alzheimer’s disease is a process. And it’s typically a combination of these three approaches: Cognitive Testing, PET biomarkers and fluid – either blood or spinal biomarkers.

In all cases, personal results are compared to norms. The person is compared to other healthy people in the population that are approximately just like them. Neurologists look at the levels of all of the things that they are measuring to determine if they think it’s Alzheimer’s disease.

And that’s how a diagnosis goes.

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Who Administers all these Neuropsychological Tests?

To get an Alzheimer’s diagnosis typically you see a specialist, like a neurologist. A neurologist may not administer all of these tests directly but he or she will interpret the cognitive test results with help from specialized colleagues.

Neurologists have special team members who administer the memory and thinking or cognitive tests. They have another team who are specialists at doing the PET imaging and interpretation of the brain scan results. And they rely on clinical laboratories to do the blood and cerebral spinal fluid testing.

Typically, the neurologist leads and coordinates these specialized teams and will interpret your test results together with your medical history to reach a diagnosis.

Can a Primary Care Physician Diagnose you?

Yes. A primary care physician (PCP) needs to be able to diagnose Alzheimer’s particularly when there’s not a neurologist practice nearby. Perhaps in some of the rural areas of the country.

But that diagnosis of Alzheimer’s from that PCP may be considered a preliminary diagnosis. Oftentimes the PCP will refer you to a neurologist to confirm their suspicions.

Many people who have memory concerns might want to start with a self-assessment test. Even though this is very hard for all humans to do, it's best to listen to your friends and family members who might be recognizing things about your memory that you don’t.
Many people who have memory concerns might want to start with a self-assessment test. Even though this is very hard for all humans to do, it’s best to listen to your friends and family members who might be recognizing things about your memory that you don’t.

Can you Self-Test for Alzheimer’s with the SAGE test?

No. The SAGE test (Self-Administered Gerocognitive Exam) is a written test for people who are at risk of dementia, or suspect they may be developing symptoms of Alzheimer’s.

These tests might be helpful to understand if you need to visit a specialist. But all of the thinking and memory testing performed for diagnostics is administered by another person to you. Don’t worry if you fail the SAGE test because it may not be Alzheimer’s disease.

Could you begin with Self-Assessment and then Consult with a Geriatrician, Neurologist or Psychiatrist?

Yes, you may start with a self-assessment test. Many people who have memory loss concerns might want to start there.

Even though this is very hard for all humans to do, it’s best to listen to your friends and family members who might be recognizing things about your memory that you don’t.

If they are expressing concerns about your memory. that’s probably a good indication to get it professionally checked by a geriatrician, neurologist or a mental health professional.

Can the MindCrowd test be Used to figure out if a Medical Consultation is Needed?

No. This is not a diagnostic test. MindCrowd is a research test, and it’s not designed to diagnose Alzheimer’s.

Don’t be afraid to take it, even if you find it difficult, because it doesn’t mean you have dementia or even mild cognitive decline. But you are helping scientists learn more about how the brain ages.

Alzheimer’s diagnostic testing looks at many aspects of how your brain works and the MindCrowd test is only looking at two particular areas: Attention and Memory.

Most Alzheimer's patients do not lose their sense of smell but some do. The loss of sense of smell is called anosmia. So, can the peanut butter test detect Alzheimer's? Click to find the answer.
Most Alzheimer’s patients do not lose their sense of smell but some do. The loss of sense of smell is called anosmia. So, can the peanut butter test detect Alzheimer’s?

Alzheimer’s Tests Myths: Can you Find the Camel?

This is a memory test where you are shown pictures of animals and you’ll be asked to name them. There’s a version of the test that shows you a picture of a camel, a rhinoceros, an elephant, among other images.

A camel may look like a horse with a hump. So if someone answers horse that would indicate a potential problem. It’s supposed to be a very easy test for someone who is not demented. But for those who are demented, the information of the images may be difficult to take in and recall the correct animal’s name.

The pictures of animals test is only 1/20th of the full Alzheimer’s dementia test. So, it won’t tell you much.

Now, if you are referring to the “find the camel in the picture puzzle” claiming to reduce the risk of dementia, that is absolutely false.

Can Smelling Peanut Butter Detect Alzheimer’s?

The peanut butter test is not how Alzheimer’s is diagnosed. Most Alzheimer’s patients do not lose their sense of smell but some do. The loss of sense of smell is called anosmia.

The problem with the peanut butter test is that Parkinson’s disease patients can lose their sense of smell too. So, failing the peanut butter test doesn’t mean you have Alzheimer’s disease. COVID or another viral infection could be hurting your sense of smell and could cause you to fail the peanut butter test. And that’s temporary.

It’s an interesting idea that has roots in some of the symptoms of the disease (Alzheimer’s dementia can affect your sense of smell) but it’s not accurate enough to replace standardized testing.

When Should you See a Doctor?

When you notice changes in cognition. Before they begin to interfere with everyday activities so that you can obtain an early diagnosis. Usually these changes are difficult to notice on your own, so pay attention to the concerns of your friends and family.

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MindCrowd is the first online research project of its kind to study millions of individuals to help bring us closer to a cure for Alzheimer’s.

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Matt Huentelman is a neuroscientist and a human genetics researcher. His laboratory studies how the brain ages and explores various ways in which we can prevent brain aging and protect against diseases of the aging brain like Alzheimer’s disease. His lab is based at TGen in Phoenix, Arizona, and he is also the lead scientist for the MindCrowd project.

MindCrowd is an internet based study of the brain that anyone 18 years of age or older can join and it can be found at

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