Scientists at Stanford University have identified a set of protein biomarkers in the blood that can correctly identify people with Alzheimer's and predict which patients with mild cognitive impairment will go on to develop the disease. If replicated in larger studies, this protein profile could drastically improve on existing methods to diagnose the disease. Because cognitive symptoms don't usually appear until the brain has undergone significant damage, and no reliable physical symptoms have yet been identified, accurate diagnosis relies largely on cognitive testing and lab tests to rule out other problems. The study was published Monday in the journal Nature Medicine.

The test is being commercialized by Satoris, based in San Francisco. In a press release issued by the company, Tony Wyss-Coray, a neurologist at Stanford University School of Medicine and company cofounder, said,

"Our data indicate blood contains a highly specific, bio­logical signature that can characterize Alzheimer's disease years before a clinical diagnosis can be made."

The blood test could also aid in the development of new treatments to stop the progression of the disease and help target those treatments to those who need them. Alzheimer's disease is usually preceded by a period of milder impairment, known as mild cognitive dysfunction. But not everyone with mild cognitive impairment will go on to develop Alzheimer's, making it difficult to test new drugs designed to stop the progression. Pharmaceutical companies are actively searching for biomarkers that predict the disease. (See "Tackling a $100 Billion Disease.")