In order to meet the challenges posed by substance use disorders, it is essential that we develop improved biomarkers to allow detection of these disorders. As reviewed by Mikeska and Craig [12], a biomarker is an objectively measurable characteristics of an organism that allows monitoring of a biological process related to normal physiology, pathophysiology, or disease. Clinically relevant biomarkers may serve a variety of purposes, such as indicating disease latency, onset, stage, response to treatment, may serve as a surrogate endpoint for intervention, or may help stratify individuals according to risk or prognosis. For maximum public health impact, biomarkers should be accurately measurable across individuals and populations. Ideal biomarkers will have high sensitivity and specificity, a high area under the curve (AUC) in a receiver-operator characteristic (ROC) analysis, and a high positive predictive value (PPV).
