Figure 2.

The definitions of a monitoring biomarker, a risk/susceptibility biomarker, and a prognostic biomarker proposed by the FDA-NIH Biomarker Working Group. The red box on the bottom presents the definition of a monitoring biomarker, and the red arrows show the role of monitoring biomarkers, which is to indicate the status or severity of disease at the time of the collection of a biomarker. The light blue box presents the definition of a risk/susceptibility biomarker, and the light blue arrows show the role of risk/susceptibility biomarkers. A risk/susceptibility biomarker measured in individuals who do not have a disease (e.g. normal cognitive function, no disease-related neurodegeneration) indicates the risk of developing a disease-related event (e.g. cognitive decline, disease-related neurodegeneration) in the future. The dark blue box presents the definition of a prognostic biomarker, and the dark blue arrow shows the role of prognostic biomarkers. A prognostic biomarker measured in individuals already having a disease or medical condition (e.g. cognitive decline, neurodegeneration) predicts the future disease progression. This figure contains images adapted from ‘Tube’ (https://smart.servier.com/smart_image/tube/) and ‘Alzheimer disease’ (https://smart.servier.com/smart_image/alzheimer-3/) by Servier Medical Art, used under CC BY 3.0.