Some researchers are using advanced imaging techniques to try to pick up protein accumulations in the brain. Others are looking for biomarkers of the disease in cerebrospinal fluid--obtained with a spinal tap--and in blood.

Satoris's detection method measures the relative abundance of particular proteins in the blood. Alzheimer's disease involves inflammation in the brain, and other research has suggested that signs of inflammation "show up in the blood as well," Buckholtz says.

Plasma contains about 30,000 different proteins, so researchers first narrowed down the field to several hundred signaling proteins. By analyzing 259 blood samples, they identified 18 proteins that are present in distinctive concentrations in the blood of Alzheimer's patients. This protein signature also distinguishes Alzheimer's from other causes of dementia, McReynolds says.

Satoris researchers are now working with other collaborators to look for blood biomarkers that could be used to track the progression of the disease. They're also trying to correlate the diagnostic biomarkers they've identified in the blood with those in the cerebrospinal fluid, as well as with the results of brain imaging.

However, until there are better treatments for Alzheimer's disease, Michelson says that diagnostic tests will be most useful as a research tool because "what's the use of confirming a diagnosis early if you can't do anything about it, if you don't have a treatment that could change what can happen?"

On the other hand, Carrillo says that a definitive diagnosis allows patients and families to plan and prepare for the future, seek out the best care and treatment, and in some cases participate in clinical trials. "That early diagnosis is critical," she says.