Delayed Recall Tests Effectively Detect Dementia.
Other useful measures include tests of verbal fluency and tests of executive function.
Dr. Salmon based his comments on results from a trial that he and his associates conducted at the Alzheimer's Disease Research Center at the University of California, San Diego, on 98 padents with early Alzheimer's disease and 98 matched controls.
Alzheimer's patients scored three standard deviations below normal on the California Verbal Learning Test, compared with controls. The test had a sensitivity of 98% and a specificity of 88%.
"When we looked at how much information the person could remember after a 20-minute delay interval, we saw a very significant deficit in the patients with
Alzheimer's compared with controls, even though they were mildly impaired Alzheimer' patients," said Dr. Salmon, a professor of neuroscience at UCSD.
The same pattern held true for tests of paragraph and figure recall. The sensitivity and specificity of these tests ranged from 86% to 89%.
"It didn't matter whether it was a verbal or nonverbal memory test," Dr. Salmon said. "Delayed recall was poor for Alzheimer's patients in both cases.
The two tests of executive function used in the study were the Wisconsin Card Sorting Test and the Trail Making Test. In the Wisconsin Card Sorting Test, patients with Alzheimer's learned fewer of the rules established by the examiner, compared with controls. In addition, they made many more perseverative errors compared with controls. "When the rules shifted, the Alzheimer's patients weren't able to shift," Dr. Salmon explained. "They continued to use the same rule over and over.
In part A of the Trail Making Test, subjects were asked to draw a line, connecting numbers as quickly as they could, as with a connect-the-dots game. In part B, subjects were asked to draw a line that shifted between numbers and letters (1-A, 2-B, 3-C, and so on). Alzheimer's patients did slightly worse than controls on part A, but significantly worse than controls on part B. The sensitivity of this test was 85%; the specificity was 83%.
Dr. Salmon and his associates used the Boston Naming Test and tests of letter and category fluency to measure language and semantic memory. In the Boston Naming Test, Alzheimer's patients scored slightly worse than controls.
In tests of letter fluency, Alzheimer's patients scored somewhat worse than their controls. But in tests of category fluency, Alzheimer's patients performed much worse than controls. The sensitivity of this test was 96%; the specificity was 88%.
Investigators used dock drawing and block drawing tests to assess visuospatial and constructional abilities. When Alzheimer's patients were asked to replicate a model of a clock on paper, they did slightly worse than controls. They also displayed slightly more impairment than controls when they were asked to draw the same clock on a blank sheet of paper, without the aid of the model.
For the block design test, investigators measured how well subjects copied a particular block pattern drawn on a piece of paper and how long it took them. Alzheimer's patients performed worse than controls on this test, but Dr. Salmon noted that the sensitivity of this test was 78%; the specificity was 79%.
"These visuospatial tasks are less effective than the other tests," he said.
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|Publication:||Clinical Psychiatry News|
|Date:||Aug 1, 2001|
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