Making the news this last week was a gene for Alzheimer’s Disease (AD). This prompted a friend to ask me, “Why would you want to know if you were going to develop the disease?” Good question. One reason is for genetic planning. Another reason is that early diagnosis may lead to earlier treatment, and thus better prognosis. After all, this approach has been successful in preventing diseases such as cervical cancer and heart attacks.

But early treatment requires early diagnosis and not all people with dementia have AD. To this end solid criteria must be developed to identify a “preclinical state.” Put another way, we need to be able to identify AD far in advance of symptoms. Genetic testing will be helpful but in itself is not sufficient.

Okay, so what test might yield such information? Probably it will come from imaging studies (MRI or PET scans) that measure the metabolism and accumulation of amyloid, an insoluble protein. Amyloid accumulates in neurons of AD patients, causing cell death. Microscopically AD patients’ brains show “tombstones,” which are small deposits of amyloid that remain after neurons die. So amyloid accumulation is likely to become one metric for defining preclinical AD, allowing people with positive family histories of the disease to be successfully diagnosed and treated.