Ray S et al. (2007) Classification and prediction of clinical Alzheimer's diagnosis based on plasma signaling proteins. Nat Med 13: 1359–1362

Early and definitive diagnosis of Alzheimer's disease (AD) could lead to better and more-targeted treatment for patients. Ray et al. have recently identified a group of plasma signaling proteins that reflect changes in the brain during the early stages of AD pathology. Levels of the 18 proteins in blood plasma can be used to identify patients with AD, or to predict the onset of AD in presymptomatic patients, with close to 90% accuracy.

First, the authors measured the relative abundance of 120 signaling proteins in an initial set of samples from 43 patients with AD and 40 controls without dementia, and through statistical analysis found significantly different expression patterns of 19 proteins (q-value <3.4%), from which a set of 18 predictors of AD was identified. When the predictors were then tested in independent samples from patients with AD (n = 42) and other types of dementia (n = 11) and controls without dementia (n = 39), patients were classified with 89% accuracy (P <0.001). Furthermore, in 47 patients with mild cognitive impairment, progression to AD was predicted with 81% accuracy (P <0.001) up to 6 years before clinical diagnosis. Functional profiling of the 18 predictor proteins pointed to involvement in systemic dysregulation of intracellular pathways of immune response, hematopoeisis and apoptosis.

Further tests are needed before this approach can be used in patients, but the identification of blood plasma biomarkers early in the course of AD could open the door to more-effective interventions.