24. Blood Test Predicts

Blood Test Predicts Alzheimer’s Up to Three Years in Advance

If Alzheimer’s disease could be detected in its early stages, before evident memory loss and functional decline, existing treatments could be started sooner, possibly with more effect. And emerging therapies might stand a greater chance of delaying symptoms. They might even cure the disease, which is projected to afflict 115 million people worldwide by 2050.

To date, tests intended to predict Alzheimer’s onset have been of limited utility. Such tests include imaging techniques, such as magnetic resonance imaging and brain amyloid imaging, and biomarker techniques, such as cerebrospinal fluid tau and amyloid-beta levels. They have failed to enjoy common clinical use because they are invasive, time-consuming, or expensive.

Now, however, a blood test that identifies 10 lipids has been used to predict Alzheimer’s onset. According to a study published March 9 in Nature Medicine, the test “predicted phenoconversion to either amnestic mild cognitive impairment or Alzheimer’s disease within a 2–3 year timeframe with over 90% accuracy.”

This study was the work of researchers centered at Georgetown University Medical Center. According to the study, which was entitled “Plasma phospholipids identify antecedent memory impairment in older adults,” the 10-lipid biopanel reflects cell membrane integrity and “may be sensitive to early neurodegeneration of preclinical Alzheimer’s disease.” That is, the blood test appears to reveal the breakdown of neural cell membranes in participants who develop symptoms of cognitive impairment of Alzheimer’s disease.

A release issued by Georgetown University indicated that the study included 525 healthy participants aged 70 and older who gave blood samples upon enrolling and at various points in the study. Over the course of the five-year study, the release continued, 74 participants met the criteria for either mild Alzheimer's disease (AD) or amnestic mild cognitive impairment (aMCI), in which memory loss is prominent. Of these, 46 were diagnosed upon enrollment and 28 developed aMCI or mild AD during the study (the latter group called converters).

In the study's third year, the researchers selected 53 participants who developed aMCI/AD (including 18 converters) and 53 cognitively normal matched controls for the lipid biomarker discovery phase of the study. The lipids were not targeted before the start of the study, but rather, were an outcome of the study.

Subsequently, the researchers validated the biopanel. In addition, they analyzed blinded data to confirm that the biopanel could match subjects with the correct diagnostic categories. Finally, they examined if the presence of the APOE4 gene, a known risk factor for developing AD, would contribute to accurate classification of the groups, but found it was not a significant predictive factor in this study.

"We consider our results a major step toward the commercialization of a preclinical disease biomarker test that could be useful for large-scale screening to identify at-risk individuals," said Howard J. Federoff, M.D., Ph.D., the study’s corresponding author and professor of neurology and executive vice president for health sciences at Georgetown University Medical Center. “We're designing a clinical trial where we'll use this panel to identify people at high risk for Alzheimer's to test a therapeutic agent that might delay or prevent the emergence of the disease."