Role of biomarkers in studies of presymptomatic Alzheimer's disease

Background: Biomarkers that have been developed largely for the study of patients with clinically diagnosed Alzheimer's disease (AD) can also be used in the study of cognitively normal individuals who may harbor underlying AD pathology. Methods: A meeting of invited experts on AD biomarkers was held on November 11 and 12, 2004 to review currently available data and to discuss unmet needs for biomarker research in presymptomatic AD. Results: Neuroimaging biomarkers have been studied to some extent in subjects at risk for AD. These imaging techniques include volumetric magnetic resonance imaging and positron emission tomography using either fluorodeoxyglucose or newer ligands that bind directly to amyloid plaque. Similarly, biochemical measures from cerebrospinal fluid or other physiologic fluids are emerging as potentially useful tools. Such biomarkers may be used either as diagnostic tools or as indicators of disease severity when followed longitudinally. A clinical diagnosis of asymptomatic individuals using biomarkers and studies involving asymptomatic subjects may raise logistical and ethical concerns. Conclusions: The technical development of biomarkers that are used for presymptomatic AD diagnosis and for longitudinally measuring disease severity is evolving rapidly. Ethical and privacy considerations must be made before such biomarkers can be applied routinely to asymptomatic populations.