How Is Alzheimer’s Disease Diagnosed?

Reviewed by: HU Medical Review Board | Last reviewed: January 2023

It used to be that the only way to get an accurate diagnosis of Alzheimer’s was by looking at the person's brain tissue after they died. Thanks to advancements in imaging, testing, and cognitive assessments, earlier and earlier diagnosis is becoming possible.1

Your doctor can get a comprehensive view of your brain and bodily health to determine if an Alzheimer’s diagnosis fits. And there are many tests that your doctor can do to help with this goal.1-3

Family history and medical history

Doctors will often first ask you about your family history and personal medical history. You should be prepared to answer these questions to the best of your knowledge. Your doctor may ask about:1,3

  • Your family's medical history
  • Illnesses you have had
  • What medicines and other drugs you use
  • How much alcohol you drink

Doctors may also ask other people in your life about your symptoms. While you are the best person to communicate your symptoms, your friends and family may have insight into how you have changed over time. Understanding when your symptoms started helps doctors understand your disease progression.2

Neurological testing

If you are concerned about Alzheimer's your doctor will probably do a mental status or neuropsychological test. There are many of these available, including the Montreal Cognitive Assessment, the Self-Administered Gerocognitive Examination, and the Mini-Mental Status Exam. These tests assess your:1,2

  • Cognitive (thinking) function
  • Memory
  • Problem solving
  • Attention
  • Use of language

These tests provide a clearer picture of your mental status. They can also show any personality or behavior changes you may not be aware of.1,2

Brain imaging

Your doctor may also perform brain imaging tests (scans), such as:1,2

  • MRI (magnetic resonance imaging)
  • CT (computed tomography)
  • PET (positron emission tomography)

MRI uses radio waves and magnets to show a detailed view of your brain, while CT uses x-rays. And PET uses something called a “tracer” to look at specific brain activity.1,2

These imaging tests are not used to diagnose Alzheimer's. But they can suggest the presence of Alzheimer’s. They can help to rule out other causes and types of brain disease. They can also establish a baseline to see how brain cells become more damaged (degenerate) as Alzheimer's progresses.1-3

Recently, a new type of imaging is being used called “volumetric MRI.” This kind of MRI looks at the volume of different brain regions to assess degeneration. Alzheimer’s disease has a specific pattern of degeneration that your doctors can see in these images.3

Genetic testing

Genetic testing can sometimes be helpful, especially for early-onset Alzheimer’s. Alzheimer’s is not exclusively a genetic disease, but it can rarely be in some people. Nearly all genetic Alzheimer’s is early-onset. This means symptoms can start as early as your 30s. Because it starts so early, early detection is also crucial.1-3

Genetic testing is usually not helpful for diagnosing Alzheimer’s in most people. But if you have a close family member who has early-onset Alzheimer’s, it can be helpful. There are primarily 3 gene mutations (changes) your doctor will look for:3

  • The AAP gene on chromosome 21
  • Presenilin 1 on chromosome 14
  • Presenilin 2 on chromosome 1

Biomarkers

There are also other tests that your doctor may perform. Blood tests, cerebrospinal fluid (CSF) tests, and other standard medical tests can help identify other causes of problems with thinking.1

Blood tests can help diagnose Alzheimer’s and rule out other conditions, like thyroid disease. Doctors can also look at the levels of tau or beta-amyloid, 2 biomarkers (biological signs) of Alzheimer’s disease. They can also do a complete blood count, metabolic panel, vitamin B12 test, and others.1-3

CSF is a colorless, watery fluid that flows around your spinal cord and brain. Your doctors can sample CSF through a minimally invasive procedure called a lumbar puncture (spinal tap). Research suggests that CSF may have elevated tau and beta-amyloid in people with Alzheimer’s.1-3

Each of these methods is helpful in diagnosing Alzheimer’s. Your doctor may use one or multiple in order to get you on the right path to care. If you are having cognitive symptoms, talk to your doctor about the best way forward for you.

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