ABSTRACT
Symptoms, body burdens, and biomarkers are observations that can be used to confirm that the cause has produced characteristic effects or that biologically relevant exposure has occurred. This chapter discusses evidence that supports the practice of diagnosis, including symptoms, body burdens, and biomarkers. Biomarker research has emphasized developing sensitive measures of effect rather than on determining the causes of observed higher–level effects. Few biomarkers or sets of biomarkers have been shown to be symptomatic of a particular causal agent. The chapter presents a discussion that organizes symptoms by the level of biological organization associated with the effect of interest at the organism, population, and community level. In most site-specific causal assessments, symptoms, body burdens, and biomarkers will be combined with other types of evidence in order to reach a causal conclusion. The weighting of symptoms is discussed even if they are not considered symptomatic, body burdens and biomarkers would be weighted using equivalent considerations.
