title: An enhancement of ROC curves made them clinically relevant for diagnostic-test comparison and optimal-threshold determination.
abstract: OBJECTIVE
  The receiver operating characteristic curves (ROC curves) are often used to compare continuous diagnostic tests or determine the optimal threshold of a test; however, they do not consider the costs of misclassifications or the disease prevalence. The ROC graph was extended to allow for these aspects.
  
  
  METHODS
  Two new lines are added to the ROC graph: a sensitivity line and a specificity line. Their slopes depend on the disease prevalence and on the ratio of the net benefit of treating a diseased subject to the net cost of treating a nondiseased one. First, these lines help researchers determine the range of specificities within which test comparisons of partial areas under the curves is clinically relevant. Second, the ROC curve point the farthest from the specificity line is shown to be the optimal threshold in terms of expected utility.
  
  
  RESULTS
  This method was applied: (1) to determine the optimal threshold of ratio specific immunoglobulin G (IgG)/total IgG for the diagnosis of congenital toxoplasmosis and (2) to select, among two markers, the most accurate for the diagnosis of left ventricular hypertrophy in hypertensive subjects.
  
  
  CONCLUSIONS
  The two additional lines transform the statistically valid ROC graph into a clinically relevant tool for test selection and threshold determination.
authors: Service de Biostatistique, Hospices Civils de Lyon, 162 avenue Lacassagne, Lyon F-69003, France; Université de Lyon, 92 rue Pasteur, Lyon F-69000, France; Université Lyon 1, 43 boulevard du 11 novembre 1918, Villeurbanne F-69100, France; CNRS, UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, Villeurbanne F-69100, France. Electronic address: fabien.subtil@chu-lyon.fr.
authors: Fabien
authors: F
authors: Subtil
authors: Service de Biostatistique, Hospices Civils de Lyon, 162 avenue Lacassagne, Lyon F-69003, France; Université de Lyon, 92 rue Pasteur, Lyon F-69000, France; Université Lyon 1, 43 boulevard du 11 novembre 1918, Villeurbanne F-69100, France; CNRS, UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, Villeurbanne F-69100, France.
authors: Muriel
authors: M
authors: Rabilloud
mesh_terms: D019540:Area Under Curve; D002648:Child; D003661:Decision Support Techniques; D003955:Diagnostic Tests, Routine / Q000706:statistics & numerical data*; D004056:Differential Threshold; D042241:Early Diagnosis; D005188:False Negative Reactions; D006801:Humans; D006973:Hypertension / Q000150:complications; D017379:Hypertrophy, Left Ventricular / Q000150:complications / Q000175:diagnosis*; D007074:Immunoglobulin G / Q000097:blood; D015233:Models, Statistical; D008991:Monitoring, Physiologic / Q000706:statistics & numerical data; D015995:Prevalence; D012372:ROC Curve; D012016:Reference Values; D012107:Research Design; D014125:Toxoplasmosis, Congenital / Q000097:blood / Q000175:diagnosis*
chemical_list: D007074:Immunoglobulin G
keywords: Decision analysis; Diagnostic test; Optimal threshold; ROC curve; Test selection; Utility