There is no clinical test to diagnose Alzheimer's Disease, or AD, and a definitive diagnosis can be made only upon autopsy. As a result, physicians use neuro-psychological assessments of cognitive function to determine possible or probable AD. Physicians use clinical tests as well to rule out other, potentially treatable, conditions to form the basis for initiating treatment. Recent research suggests a test of spinal fluid can identify AD years before symptom onset.
Alzheimer's Disease
AD is a progressive disorder in which certain types of nerve cells in the brain degenerate and die. Its causes are unknown. According to the Alzheimer's Organization, the clinical symptoms associated with AD include memory loss, language disorders, visual-spatial impairment and behavioral disturbances. Individuals with AD may present with various mosaics of impairment, but all have difficulties with memory.
Diagnosis
According to the National Institute on Aging, there is no clinical test to diagnose AD. However, to diagnose probable AD, the American Psychological Association's Diagnostic and Statistical Manual, 4th. Ed. recommends documenting the following: Multiple cognitive deficits that are evident in both memory impairment and at least one other cognitive impairment such as language disturbance. The cognitive disturbances cause significant impairment in social or occupational functioning and represent a significant decline in previous functioning. The course of cognitive impairment is characterized by gradual onset and continuing decline. Other causes of the cognitive deficits are ruled out.
Neuro-psychological Assessments
A key element of diagnosing AD is a neuro-psychological assessment. These exams have been shown to be specific and sensitive to AD and are important tools not only in the initial diagnosis, but also in monitoring the progression of the illness.
Several neuro-psychological assessment tools are available. One commonly used is the Mini-Mental Status Exam, or MMSE, which consists of a series of simple questions and tasks. For example, it includes assessments of one's orientation to time and place (What season is it? What county are you in?); immediate and delayed recall of a list of items; attention (ability to spell a word backwards, for example); ability to follow commands; and reading, writing, and copying exercises. The MMSE is scored, with a score of less than 20 out of 30 correct indicative of impairment.
Genetic Testing
Having a parent or sibling with AD increases one's risk slightly over that of the general population. Four genes have been associated with AD. Three have been associated with the rare form of early onset AD, which has symptoms appearing in a person's early 40s and mid-50s. Since families with a history of early onset AD are already aware of the risk, it is unclear what added benefit genetic testing would add.
According to the Alzheimer's Association, the fourth gene, APOE-e4, is linked to the more common form of AD appearing after age 55, usually significantly after. Here, too, the rationale for testing is unclear and controversial. Most people who develop AD do not have this genetic mutation. In addition, not everyone with APOE-e4 will go on to develop AD, there are no proven ways to reduce your risk of developing it and there is significant anxiety associated with a positive test.
Recent Research
Much research is underway to develop early and more specific tests for AD to better understand the illness and, perhaps, to aid in developing earlier treatments. In August 2010, "The New York Times" reported on a study that found a test of spinal fluid proteins could identify with 100 percent accuracy individuals who had AD as well as those with mild memory loss who went on to develop AD. These results are not ready to be translated to clinical tests but will likely aid in a better understanding of the illness.
References
- National Institute on Aging: Alzheimer's Disease Fact Sheet
- Alzheimer's Organization: Diagnosing Alzheimer's
- Alzheimer's Research Forum: Neuropsychological Testing
- "Archives of Neurology"; Diagnosis-Independent Alzheimer Disease Biomarker Signature in Cognitively Normal Elderly People; Geert De Meyer, Ph.D.; Fred Shapiro, MLS; Hugo Vanderstichele, Ph.D. et al.
- New Mexico Aging and Long-Term Services Department: Mini-Mental Status Exam
