Diagnosis of Alzheimer’s Disease

There are no laboratory tests to confirm a diagnosis of Alzheimer's disease. However, your doctor will be able perform a thorough clinical evaluation and conduct tests that will provide a diagnosis with a 90% accuracy rate, and will rule out other potential conditions.

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 forms of dementia. These tests typically include:

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

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

Psychological Testing—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.

CT and MRI Scan—Your doctor may suggest tests, such as computed tomography (CT) or magnetic resonance imaging (MRI) , which will take an x-ray 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.

Brain MRI Scan

© 2008 Nucleus Medical Art, Inc.

PET ScanPositron emission tomography (PET) is a special type of brain imaging scan that involves use of special radioactive compounds. It is expensive and not widely available, but often PET scans provide valuable information that CT/MRI scans cannot provide. In addition, Medicare and other insurers will cover the cost of a PET scan in certain cases.

Though not routine, a lumbar puncture to test the cerebrospinal fluid (CSF) and an ophthalmologic screening can be done to investigate for other atypical dementias. Additionally, EEG (electroencephalogram) is a test that measures and follows the electrical activity of the brain. This is not a routine test for dementia, but may be used in investigation and diagnosing atypical dementias.

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

Probable Alzheimer’s—This indicates that other dementia-related disorders have been ruled out, and that the symptoms are likely due to Alzheimer’s disease. This is based on the Mini Mental Status Exam, with at least 2 areas of cognition affected, worsening of memory, and impairment of activities of daily activities.

Possible Alzheimer’s—The dementia is caused by Alzheimer’s disease, but there may be other disorders present that may change the progression of the Alzheimer’s disease in a manner that is somewhat atypical from just Alzheimer’s disease.

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.

References:

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



Last reviewed April 2007 by Roshni N. Patel, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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