Alzheimer's Disease Diagnosis

Diagnostic Tests

There are no laboratory tests to confirm a diagnosis of Alzheimer's disease. However, your doctor will be able do a thorough clinical evaluation and conduct tests that will provide a diagnosis with a relatively high accuracy rate, and other potential conditions will be ruled out.

Initially, the doctor will ask about your symptoms and medical history, and perform a physical exam. Tests to rule out other conditions may include:

Blood and Urine Tests

This may be done to rule out other causes of dementia. These tests may include:

• Electrolytes (eg, sodium, potassium, and calcium)
• Thyroid function tests
• Complete blood count (CBC)
• Levels vitamins (including B vitamins)
• Erythrocyte sedimentation rare (ESR)
• Lyme disease test
• HIV test
• Vasculitis work up

Genetic Tests

Genetic tests are being offered for people with family members with early-onset Alzheimer’s.

Other Tests

• Neurological exam—This exam tests the nervous system (brain, spinal cord, nerves, and muscles) for evidence of other neurological disorders.

• Psychological evaluation—Pyschological testing is used to rule out depression or other emotional illnesses that may often be the first sign of Alzheimer’s disease.

• Neuropsychological evaluation—This evaluation tests language, memory, reasoning, judgment, and orientation, and may assist in the diagnosis of Alzheimer’s disease in the early stage or indicate other causes of dementia.

• Mental status testing—This testing is used to evaluate memory, sense of time and place, and problem-solving abilities, attention span, language skills, visual spatial perception, learning capacity, judgement, insight, and decision making skills. This is often a part of the Neurological examination and Neuropsychologic testing.

• CT and MRI scan—Your doctor may suggest tests, such as CT scan or MRI , which will take a picture of your brain. These scans may help to identify any abnormalities in the brain, which may indicate Alzheimer’s disease or point to other causes of dementia. Special MRI sequences (eg, funtional MRI) are also being investigated for evaluating Alzheimer’s.

• PET scan— PET scan is a special type of brain imaging scan that involves use of special radioactive compounds.

Though not routine, a lumbar puncture (spinal tap) to test the cerebrospinal fluid (CSF) and an ophthalmologic screening can be done to investigate for other atypical causes of dementia. Additionally, electroencephalogram (EEG) is a test that evaluates and follows the electrical activity of the brain. This is not a routine test for evaluating dementia.

Diagnostic Categories

A diagnosis of Alzheimer’s disease usually falls into one of three categories:

• Probable Alzheimer’s—This indicates that other dementia-related disorders have likely been ruled out, and that the symptoms are likely due to Alzheimer’s disease. At least two areas of cognition are affected; one is worsening of memory.

• Possible Alzheimer’s—The dementia is possibly caused by Alzheimer’s disease. But, there may be other disorders present that may be the underlying cause of the dementia.

• Definite Alzheimer’s—This diagnosis can only be made at the time of death through an autopsy, when a pathologist can study the brain tissue. This is the only way to diagnose the disease with complete certainty.

• Screening for Alzheimer’s Disease

References:

Alzheimer’s Association website. Available at: http://www.alz.org/ .

Hampel H, Frank R, Broich K, et al. Biomarkers for Alzheimer’s disease: academic, industry and regulatory perspectives. Nat Rev Drug Discov.2010;9(7):560-574.