text: Predictive biomarkers measure the effect of a drug and tell if the drug is having its expected activity, but do not offer any direct information on the disease.  Predictive biomarkers are highly sensitive and specific; therefore they increase diagnostic validity of a drug or toxin's site-specific effect by eliminating recall bias and subjectivity from those exposed. For example, when an individual is exposed to a drug or toxin, the concentration of that drug or toxin within the body, or the biological effective dose, provides a more accurate prediction for the effect of the drug or toxin compared to an estimation or measurement of the toxin from the origin or external environment.