Receiver Operating Characteristic (ROC) curves are used in medical research as a graphical display for the relationship between sensitivity and specificity for a continuous test variable. In a ROC curve the sensitivity is plotted against 1-specificity for every cut-off point of the diagnostic variable. Although often shown as an overall measure of test performance, the ROC curve has no direct clinical interpretation. To be applicable for clinical practice, a cut-off value should be chosen, balancing sensitivity, specificity, the severity of the disease under study, availability of treatments, as well as consequences from false positivity and false negativity in terms of costs, psychological impact and effect on health outcomes. Copyright © 2011, Nederlandse Vereniging voor Intensive Care.