Alzheimer's Diagnosis: How do you know for sure?

Currently there are no definitive tests to determine an Alzheimer's diagnosis, except for an autopsy which may be performed after death. Instead, the current approach for establishing an Alzheimer's diagnosis basically involves a process of elimination, ruling out other conditions which may mimic or exacerbate memory conditions such as depression, Huntington's disease, or hypothyroidism. An Alzheimer's diagnosis is essentially made based upon data from the patient's history, mental status exams and interviews with the patient, family members and friends over a period of time. Studies have indicated that a diagnosis of Alzheimer’s disease based upon such clinical features are accurate in about 90% of the cases. According to the Diagnostic and Statistical Manual of Mental Disorders (DSM- IV), among other things, a combination of memory impairment and other cognitive deficits, such as difficulty communicating which is severe enough to affect social and job functioning must be found as well as a memory decline which is determined to be gradual in onset.

Although slightly less important than clinical features in making an Alzheimer's diagnosis, laboratory imaging studies are also useful in providing additional information. Laboratory tests look for certain proteins or genes associated with Alzheimer's disease while imaging techniques examine the brain for shrinkage. There is no foolproof test currently available including having a genetic predisposition to Alzheimer's disease. Genetic predisposition does not mean that a specific individual will develop the disease and coincidentally many normal brains exhibit shrinkage.

Laboratory tests for an Alzheimer's disease diagnosis:

Recently, two new tests have been developed called the ADmark Assays. One of these assays measures beta-amyloid and tau protein in the spinal fluid (requiring a spinal tap). The other assay considers the probability that an individual’s dementia is due to Alzheimer's disease based upon whether the specific form of the gene that makes APOE (designated as e4) is present in the individual’s system. This test is usually discouraged in asymptomatic individuals, however. According to a panel of experts assembled by the National Institutes of Health, testing for this APO e4 gene should not be performed currently because there is presently no cure for Alzheimer's disease as well as no treatment that has been recommended to lower the risk of developing it. It is believed that knowledge of the gene’s presence could produce unnecessary anxiety in an individual and can lead to discrimination by employers or health insurance companies.

Alzheimer's diagnosis and imaging studies:

Imaging studies may eventually aid in the Alzheimer's disease diagnosis before the onset of symptoms. Positron emission tomography (PET), single photon emission computer tomography (SPECT) and magnetic resonance imaging (MRI) scans are all currently used to examine brain structure or function in Alzheimer's disease patients. Currently however, the scans are not routinely used in Alzheimer's diagnosis, although they can rule out other possible causes of dementia.

Information from The Johns Hopkins Medical Guide to Health After 50

Additional information and webpage by Paul Susic M.A. Licensed Psychologist Ph.D Candidate (Geriatric Psychologist)

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