Consider a battery of markers that reflect a wide array of physiologic functions and genetic damage and relate a particular marker in question to others in the battery. Each proposal submitted in response to this solicitation should include studies to evaluate the effectiveness of the proposed biomarker in quantifying the event or condition of interest. To evaluate the use of a biologic measurement as a biomarker, it is necessary to understand the relationship between the marker and the event or condition of interest. Determining the specificity and sensitivity are critical components of the evaluation process. Specificity refers to the ability of a measurement to effectively identify negative responses in order to minimize the number of false positives.
Sensitivity refers to the ability of a measurement to detect positive responses.
One of the purposes of biomarkers in environmental health research is to identify highly exposed individuals or groups, so that risk can be predicted and disease prevented. Therefore, biomarkers must not only be evaluated in terms of their ability to assess the presence or absence of an exposure or disease, but also on their ability to quantify the exposure, dose, or level of disease. Appropriate validation for a biomarker depends on its anticipated use. A biomarker observed well before the onset of disease may have a low predictive value as a biomarker of effect, but be very useful as a biomarker of exposure, enabling long-term surveillance of an exposed population. In contrast, a biomarker of effect that is expressed long after exposure could be of relatively little use in exposure assessment, but be very useful in predicting progression of disease or in calculating risk.