No single tests for Alzheimer’s Disease (AD) can accurately diagnose the condition. However, doctors can reach a diagnosis with 90 percent accuracy by eliminating other possible conditions. Because other treatable conditions, such as fluid buildup in the cavities of the brain or thyroid disease can also cause dementia, careful examination is critical before diagnosing AD. Screening for Alzheimer’s disease requires a neurological exam as part of a complete physical exam that includes a review of the family history.
How is Alzheimer’s Disease Diagnosed?
Doctors may prescribe a number of different tests for Alzheimer’s disease to eliminate other potential causes of symptoms. These may include:
- lab tests of the patient’s blood, urine and spinal fluid
- mental status testing of memory, cognitive and thinking abilities
- neuropsychological testing
- blood tests
- chest x-rays
- EEG (electroencephalogram) to record brain activity
- genetic testing
Brain imaging using CT (computed tomography) scan and MRI (magnetic resonance imaging) can reveal brain tumors, evidence of stroke, excess fluid in the cavities (ventricles) of the brain and other causes of dementia. During very early stages of AD, brain scans can be normal; as the disease progresses, an MRI may reveal areas of the brain that have decreased in size.
The only test for Alzheimer’s disease that is completely accurate is to examine the brain tissue. The brains of people with AD commonly have neuritic plaques (clusters of dead cells and proteins) and neurofibrillary tangles (twisted fragments of protein that clog nerve cells). Unfortunately, these changes can only be observed during an autopsy.