A simple ELISA test was quite accurate in identifying presymptomatic AD in this small, industry-funded study.
It has been difficult to develop tests to diagnose Alzheimer disease (AD) noninvasively and years before dementia develops. Cognitive testing is helpful but imperfect, as are recently developed imaging studies, tests of cerebrospinal fluid, and blood tests. Now, an industry-funded international team reports the development of a new and simple ELISA (enzyme-linked immunosorbent assay) blood test.
The researchers studied blood plasma from 85 individuals with AD and 79 nondemented controls. They assayed for 120 known signaling proteins in a "training set" comprising half of the AD and non-AD patients, and found a group of 18 proteins that distinguished AD patients from the controls. These 18 proteins were then used in a new "test set" comprising the rest of the AD patients and controls, as well as individuals with other dementias: The proteins predicted AD patients with 90% accuracy and non-AD patients with 88% accuracy.
In a separate analysis, the proteins were 91% accurate in identifying patients with mild cognitive impairment who went on to develop AD within 2 to 5 years, and 100% accurate in identifying patients with mild cognitive impairment who developed non-AD dementia.
Comment: This report suggests that a simple blood test may be quite accurate in identifying presymptomatic AD. However, larger studies — performed by teams independent of the company that developed the test — are needed to confirm the accuracy and utility of the test.
Published in Journal Watch General Medicine December 4, 2007
Ray S et al. Classification and prediction of clinical Alzheimer’s diagnosis based on plasma signaling proteins. Nat Med 2007 Nov; 13:1359.