Better Tool for Diagnosing Alzheimer’s Disease
“The apolipoprotein E genotype may be undeniable as a genetic risk factor for Alzheimer’s disease, but its use as a diagnostic aid has received little attention until now,” says Dr. Richard Mayeux, senior author of a report on findings published in the New England Journal of Medicine in February. Dr. Mayeux, Gertrude H. Sergievsky Professor of Neurology, Psychiatry and Public Health (epidemiology), calls the study the largest cooperative investigation to date and shows for the first time the usefulness of ApoE testing in diagnosis and treatment of Alzheimer’s. The work, in collaboration with the National Institute on Aging, collected research findings from 26 federally funded Alzheimer’s Disease Centers nationwide. Researchers found that results from the ApoE-4 genetic test, which detects the presence of the ApoE gene in the DNA of a patient’s blood, alone are inconclusive and do not provide sufficient evidence to diagnose Alzheimer’s disease. However, when the ApoE test is administered along with a thorough examination the validation of the clinical diagnosis of Alzheimer’s disease could be greatly improved. Investigators reviewed the eligibility of men and women referred nationwide to Alzheimer’s Disease Centers for diagnosis of dementia, examining records of 1,108 women and 1,080 men. Each patient underwent a battery of clinical and behavioral tests, followed by numerous laboratory and brain imaging studies. The patients were followed throughout the course of their disease. Based on brain autopsies Dr. Mayeux found that 93 percent of the patients whose brains showed clear evidence of Alzheimer’s-related changes had been diagnosed by a physician as having the disease. However, 45 percent of those found to have other forms of dementia at the time of brain autopsy also had been diagnosed by physicians as having Alzheimer’s. This high rate of false positives shows the limitations of using recommended clinical criteria alone. When the ApoE genotype was used alone in patients who first met clinical criteria for Alzheimer’s, false positive rates decreased from 45 percent to 16 percent. The addition of ApoE genotyping to an arsenal of other tests used to determine Alzheimer’s status may be useful, but Dr. Mayeux cautions that the study was “done in a selected group of people who receive treatment in specialized centers for Alzheimer’s disease. More broad-based study is needed before these results can be assumed to be universally applicable.” Other Columbia authors were Drs. Steven Shea and Ming-xin Tang. Return to Contents |
A test for the apolipoprotein E (ApoE) genotype combined with a thorough clinical evaluation may help confirm a diagnosis of Alzheimer’s disease.