Exams and Tests
Alzheimer's disease is diagnosed after other conditions are ruled out. If you are suffering from a decline in mental abilities (dementia), your doctor will attempt to find out if another treatable condition may be causing those symptoms.
- It is very important to rule out delirium as a possible cause of symptoms, especially if the symptoms came on suddenly rather than gradually. Delirium may require emergency medical attention.
- Symptoms of confusion and memory loss can sometimes be caused by depression. Depression is very common among older adults, but it is sometimes difficult to recognize. It may be successfully managed with medicine and counseling.
Alzheimer's disease is diagnosed with a medical history and a physical exam. A physical exam is used to help find out if a physical problem may be causing a person's dementia symptoms. It may be possible to correct some of these problems. For example, sometimes a simple hearing or vision problem can cause confusion, social withdrawal, or a change in behavior, such as hostility or unresponsiveness. The person may have an undiagnosed illness or infection that is causing the symptoms.
In addition, the doctor will do a mental and functional status exam and a mental health assessment. During these exams, the person will be asked to perform simple tasks that check orientation. It usually is helpful to have a family member or someone in close contact with the person present at the appointment. A family member may be able to provide the best information about how a person's day-to-day functioning, memory, and personality have changed.
Brain imaging tests such as CT scans and magnetic resonance imaging (MRI) may also be done to make sure another problem is not causing the symptoms. Positron emission tomography (PET) or single photon emission tomography (SPECT), two other imaging tests, are not routinely done but may be useful in individual cases.
A small number of people with dementia have a condition that proper treatment can reverse (unlike Alzheimer's disease). Lab tests may be done to rule out other possible causes of a person's symptoms, such as levels of certain minerals or chemicals in the blood that are too high or too low, liver disease, abnormal thyroid levels, or nutritional problems, such as folate or vitamin B12 deficiencies. Treatment for these conditions may slow or reverse mental decline.
Blood tests often done to check for these conditions include:
- Complete blood count (CBC), which shows the kinds and number of cells in your blood to help your doctor evaluate your symptoms.
- Liver function tests (AST, ALT, alkaline phosphatase, bilirubin), which detect liver damage or disease.
- Folate (folic acid) test, which detects the level of the B vitamin folic acid either in plasma (the liquid part of blood) or in the red blood cells. Folic acid is needed for the production of both red and white blood cells.
- Vitamin B12 concentration, which detects the level of vitamin B12 in your blood. Vitamin B12 is needed to produce red blood cells and to maintain a healthy nervous system.
- Electrolyte and blood glucose levels (sodium, potassium, creatinine, glucose, calcium), which are needed to keep the body's balance of fluids at the proper level and to maintain normal functions, such as heart rhythm, muscle contraction, and brain function.
- Thyroid function tests. Abnormal thyroid hormone levels are a common cause of forgetfulness, confusion, lethargy, and other symptoms of dementia in older people. Medicine can easily improve symptoms if a thyroid problem is present.
- Human immunodeficiency virus (HIV) infection test, if the person has risk factors for HIV or the medical history suggests it. Untreated HIV can cause symptoms such as personality changes or problems concentrating.
- Brain imaging tests such as a CT head scan or an MRI of the head may be done to rule out other causes of symptoms when the diagnosis is unclear.
- A test that measures electrical activity in the brain called an electroencephalogram, or EEG, may be done if the medical history suggests a seizure disorder.
In some cases, examining the brain after death (autopsy) is done to look for changes in the brain that may show Alzheimer's disease. An autopsy is the only definite way to diagnose Alzheimer's disease, but the illness may not be clearly identified if the autopsy is performed when someone dies during the early stages of the illness. An autopsy is rarely necessary, but may be done if the family wants to confirm that the person had Alzheimer's disease.
At this time, there is no routine screening for Alzheimer's disease. It is difficult to diagnose Alzheimer's disease in its early stages. This does not mean that you should ignore symptoms of mental decline (dementia) or assume that they are a normal part of aging. Talk to your doctor if you are concerned about memory loss or other symptoms of dementia, such as having difficulty finding your way around familiar places.