Blood Test for Alzheimer’s Yields Promising Preliminary Results

Thu, 13 Oct. 2011 - 12:53 a.m. MT
Credit: ARA Staff - American Running Association

In mid-October scientists announced the development of a blood test that can accurately diagnose Alzheimer's disease years before debilitating memory loss occurs.

The test, which was developed at Stanford University, is 90 percent accurate and distinguishes the blood of people with Alzheimer’s from the blood of those without the disease. The test was about 80 percent accurate in predicting which patients with mild memory loss would go on to develop Alzheimer’s disease two to six years later.

The medical community is calling the results very promising but nevertheless preliminary. The work must be validated by larger studies, in particular because there have been many disappointments in the past. The search for “biomarkers” in Alzeheimer’s disease diagnostics is furtive and ongoing, and often leads to early announcements that don’t always live up to their expectations.

Alzheimer’s is currently diagnosed by a battery of mental and other tests, an inevitably subjective process. Doctors agree that it would be very useful to have something like a pregnancy test for Alzheimer’s—one that is simple and definitive and can pick up the disease very early, maybe even before symptoms appear.

People do not agree universally about the value of early diagnosis for Alzheimer’s disease, due to the present ineffectiveness of treating it. Some people simply do not want early notification that they have an incurable ailment. But other people want to know what their future holds so they can plan their estates and other aspects of their lives. However that aspect of early diagnostics plays out on an individual basis, the real usefulness of such a test comes once drugs are developed that slow or halt the progression of the disease, several of which are now being tested. The drugs would be most valuable if they could be used before cognitive ability has declined too much.

The Stanford group found evidence from animal studies that brains affected by Alzheimer’s send out signals to the body’s immune system. The team decided to focus on proteins in the blood that are involved in communication between cells, hoping to eavesdrop, as it were, on “dialogue” related to Alzheimer’s. The researchers gathered over 200 blood samples from people with Alzheimer’s and those without. Using 83 of the samples, they measured the abundance of 120 proteins involved in cell signaling and found they could distinguish the Alzheimer’s samples from the controls using 18 of the proteins. They then tested their 18-protein signature on another 92 samples. The tests agreed with the clinical diagnosis about 90 percent of the time.

Based on samples from 47 patients with mild cognitive impairment, the researchers were also able to predict with roughly 80 percent accuracy whether a patient went on to develop Alzheimer’s two to six years after the blood sample had been collected.

(“Progress Cited in Alzheimer’s Diagnosis,” by Andrew Pollack, New York Times, Oct 14, 2007)

(RUNNING & FITNEWS^®September / October 2007 • Volume 25, Number 5)