How is Alzheimer's Disease Diagnosed?

Some degree of memory loss or impairment is common as you age. However, Alzheimer's disease causes more severe memory loss and cognitive impairment. An accurate diagnosis of Alzheimer's disease is crucial for treatment and care. It is also important for making long-term plans.

Currently, a definitive diagnosis of Alzheimer's disease requires an exam of brain tissue, which is very rarely done while a person is alive. However, there are many clinical findings and tests that can support a likely diagnosis of Alzheimer's disease. Many of these tests help rule out other medical conditions that can cause similar symptoms.1

Medical history

If you are experiencing cognitive symptoms or memory issues, it is important to talk to your doctor. They will ask you questions about:1

  • Your medical history
  • Any other medical conditions you have
  • Your symptoms
  • How your symptoms impact you

They will also likely do a physical exam. This is to see if there is another medical condition that could be causing your symptoms. This could include things like:1,2

  • Infection
  • Side effects of medicines you are taking
  • Sleep disorders
  • Parkinson's disease
  • Stroke

If more testing is needed, your doctor might send you to a specialist.1,2

Neurological tests

Specialists may conduct a variety of other tests to look for signs of brain issues. These may include:2

  • Mental status testing
  • Neuropsychological testing
  • Biological testing
  • Talks with friends and family

This helps provide them with a broader picture of your mental status. They can also show any personality or behavior changes that you might not know of. These could be relevant to a diagnosis of Alzheimer's or another condition.2

Lab tests might be done to rule out things like a thyroid disorder or low vitamin B-12 levels. Both of these can cause symptoms similar to Alzheimer's disease.2

Brain imaging

One of the main effects of Alzheimer's disease is the destruction of brain cells. This can show up on brain imaging tests. Imaging tests may be done to see if these changes are apparent on the scan. They also can rule out other things, such as a brain tumor, hemorrhage, or other brain diseases.1,2

Brain imaging tests that may be done include:2

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

However, brain scans alone are not enough for a diagnosis of probable Alzheimer's disease. Age-related changes in the brain can look similar to abnormal changes seen in Alzheimer's and other dementias. While helpful, scans alone are not a perfect diagnostic tool. They are helpful, however, in ruling out other conditions.2

Biomarkers

Currently, a definitive diagnosis of Alzheimer's disease is only possible following an exam of brain tissue, usually after death. However, there is hope that may soon change. Many research labs are looking for biological signs of Alzheimer's disease that can be measured with a lab test. These tests look for things called biomarkers.3

For example, blood tests have been developed that can detect levels of beta-amyloid protein. This protein builds up in the brain of people with Alzheimer's disease. This and other biomarkers may one day help doctors make a more definitive diagnosis of Alzheimer's disease.1

Looking at a range of biomarkers may also help track disease onset and progression. Biomarkers provide an opportunity for researchers to detect concrete changes in the brain. This can help with early-detection measures, which can improve drug efficacy and day-to-day activity.1

The future of biomarkers is promising. Researchers are looking into more biomarker tools. These include spinal fluid testing and a wider range of blood tests.3

Biomarkers can also be helpful in testing new drugs for Alzheimer's. Future testing focuses on less invasive and less expensive procedures for a wider range of people with symptoms of Alzheimer's.

Getting an accurate Alzheimer's diagnosis

Getting an accurate diagnosis of Alzheimer's can be helpful for both you and your loved ones. Not knowing why you are having symptoms can be scary and stressful. A diagnosis helps give you a plan and resources.

It also helps connect you and your family with other people living with the disease. This allows you to get support and learn from each other. It also provides you, your family, and caregivers with the opportunity to learn about the disease. You can make a plan for the future. You may also be able to participate in clinical trials or studies.

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Written by: Katharine Henn | Last reviewed: November 2021