A test to reliably detect Alzheimer's before its clinical symptoms become apparent may be one of the best things we can do to help those who suffer from the disease, and yet this goal has been elusive. The current methods of diagnosing Alzheimer's, which involve ruling out other sources of cognitive decline, are time-consuming and ultimately leave the doctor to judge whether or not the symptoms indicate Alzheimer's or something else. Researchers continue to search for an effective blood test, and their work may allow an earlier and more definitive diagnoses.

Stanford researchers have been at the forefront of the search for a reliable blood test, and an October 2007 study published in Nature Medicine provided promising results. A team led by Dr. Tony Wyss-Coray was able to accurately predict an Alzheimer's diagnosis about 90% of the time using 120 cell-signaling proteins found in plasma and 18 distinct proteins. The blood test was about 80% effective at identifying those with mild memory loss who would develop Alzheimer's in two to six years.

Because Alzheimer's is generally not diagnosed until after the individual has experienced cognitive decline, the disease usually causes significant damage to the brain before it is even diagnosed. An estimated 1.8 million Americans have the disease but have not been diagnosed. Developing a way to definitively diagnose Alzheimer's earlier is one of the most important things we can do to improve the treatment of those who will develop the disease.