indicates clinical effect of monitors effect of The level of prostate-specific antigen (PSA) monitors_effect_of therapies applied for the treatment of prostate cancers. Clarification: An 'exposure agent' can be either a medical product or some substance (e.g., pesticide) , physical factor (e.g., radiation), or organism (e.g., virus) that originates from the environment. Basis: This relation is based on the 'BEST' classification of and definition for 'biomarker', as given by the FDA-NIH Biomarker Working Group: A defined characteristic that is measured as an indicator of normal biological processes, pathogenic processes, or biological responses to an exposure or intervention, including therapeutic interventions. The BEST classification includes diagnostic, prognostic, susceptibility/risk, monitoring, predictive, safety, and pharmacodynamic/response biomarkers. See PMID:29405771 for details. Note that any given biomarker can be of a different type in different contexts. https://orcid.org/0000-0001-5809-9523 A relationship between a serially-measured biomarker 'b' and an exposure agent 'e', where 'b' is used to provide evidence of a biological effect of 'e'. Darren A. Natale