Alzheimer's Disease: Tests

There is no a single test for diagnosing Alzheimer's disease. Your doctor can only diagnose probable Alzheimer's disease after a thorough medical, psychiatric, and neurological evaluation, to rule out all other possible causes of dementia. Alzheimer's disease cannot be positively diagnosed until after death, when the brain can be closely examined for certain microscopic changes caused by the disease. However, through thorough testing and a "process of elimination," doctors today can diagnose probable Alzheimer's with almost 90 percent accuracy. Diagnosing Alzheimer's often entails:
Taking a detailed medical history
Performing general and neurological examinations
Giving specific tests that measure cognitive skills
Performing certain blood studies
Analyzing images of the brain
This section has more on:
Why dementia should be evaluated by a doctor
What your doctor may well do first
Tests your doctor might recommend
Why dementia should be evaluated by a doctor
An early and accurate diagnosis of the cause of dementia is important for the following reasons:
To identify any treatable condition and initiate treatment as appropriate
To rule out Alzheimer's disease and so ease the patient's and his or her family's concern
To identify Alzheimer's disease at the earliest possible stage, which gives the patient and family time to plan for the future needs and care of the patient
Alzheimer's disease is the single most common form of dementia, but a number of other causes are also known, some of which may be at least partially reversible. Evaluation for dementia includes a search for alternative causes--chemical or metabolic disorders such as hypothyroidism or vitamin B12 deficiency, effects of chemical substances including tranquilizers and alcohol, depression, and structural processes such as tumors, strokes, or enlargement of the ventricles (fluid sacs) within the brain.
In addition, some Alzheimer's disease symptoms--such as incontinence and depression--can be effectively treated. Therefore, it is very important to diagnose the cause of the dementia early and correctly.
What your doctor may well do first
The following diagnostic tools may be used to help make a diagnosis of Alzheimer's disease:
Patient history: A patient history helps the doctor assess an individual's past and current health situation. It also helps the doctor evaluate any medical problems, develop a plan of treatment, and monitor the patient's health over time. During this evaluation, the doctor asks the patient a series of questions. A thorough patient history includes:
Patient's identifying information
Chief complaint
History of current illness
Past medical history
Current health status
Psychosocial history (marital status, living conditions, employment, sexual history, significant life events)
Mental status
Family history (including any illnesses that seem to run in the family)
Review of symptoms
Physical exam: The physical examination is part of the patient care process. The exam enables the doctor to assess the overall physical condition of the patient. If the patient has a medical complaint, the physical exam provides the doctor with more information about the problem, which helps the doctor determine an appropriate plan of treatment. The physical exam includes an evaluation of the following:
Vital signs (temperature, blood pressure, pulse)
Height and weight
Skin
Head, eyes, ears, nose
Throat/neck
Chest, including lungs and heart
Breasts
Abdomen
Bones and muscles
Nerves
Rectal/genital area
Chest X-ray (may be used by the doctor to help rule out other disorders that may be causing symptoms similar to those of Alzheimer's disease)

In a large study of twins, Alzheimer's disease appears to be highly heritable and genetic factors may also influence timing of the disease, according to an article in the February Archives of General Psychiatry, one of the JAMA/Archives journals.

PLD1 protein is implicated in Alzheimer's brain damage