Diagnosing Alzheimer's disease will one day be accomplished with biological markers, such as tests of blood or spinal fluid. Already several biomarker tests are in development. But a new study shows that, for now, the old-fashioned cognitive tests using pen and paper are the most accurate.
Researchers looked at 116 people with mild cognitive impairment who developed Alzheimer's disease in two years, 204 people with mild cognitive impairment that did not develop the disease and 197 cognitively healthy people.
They used a variety of neuropsychological tests to assess the individuals' cognitive abilities and also obtained spinal fluid and a blood sample for biomarker tests. Finally, the participants had brain scans.
The study, published Monday in the Archives of General Psychiatry, found two measures on brain scans that were indicative of a higher probability of declining from mild cognitive impairment to Alzheimer's disease. But a change in the participants' scores on tests that measured functional ability showed a larger rate of decline than did any changes in biomarkers. Two specific cognitive tests — the Functional Assessment Questionnaire and the Trail Making Test, part B — appeared to predict most accurately whether an individual would develop Alzheimer's disease.
Biomarkers, said the authors of the study, "may be most informative in very early prodromal stages, a perspective that has been incorporated into proposed diagnostic criteria for preclinical AD."
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