Alzheimer’s Isn’t Up to the Tests

By SANJAY W. PIMPLIKAR
NYT

CLEVELAND

A PANEL of medical experts from the National Institute on Aging and the Alzheimer’s Association last week proposed changes in the way doctors diagnose Alzheimer’s disease — including the use of so-called biomarkers, tests like PET brain scans and analyses of spinal fluids to promote early detection of the disease. Although these recommendations are well intentioned, evidence suggests that it would be a mistake to adopt them at this time. To understand why, it’s important to recognize what these tests mean, in what context the information will be used and what experience has shown us.

First, about the diagnostic tests: A PET scan detects clumps of a deformed protein called amyloid beta, commonly known as plaques. The presence of these plaques has been a gold standard of Alzheimer’s pathology since 1906, when Dr. Alois Alzheimer first identified them in a patient.

However, we now know that roughly one-third of all elderly adults have such plaques in their brains yet function normally. And eleven clinical trials, recently made public by a group of drug companies, that were aimed at reducing these plaques in Alzheimer’s patients all failed to show cognitive improvement, even when the brains were cleared of plaques.

Thus, the presence of plaques cannot predict with any accuracy or specificity that an individual is going to acquire the disease — and researchers are increasingly looking beyond the amyloid hypothesis for an adequate explanation for Alzheimer’s.

(More here.)