title: Diagnostic methods I: sensitivity, specificity, and other measures of accuracy.
abstract: For most physicians, use of diagnostic tests is part of daily routine. This paper focuses on their usefulness by explaining the different measures of accuracy, the interpretation of test results, and the implementation of a diagnostic strategy. Measures of accuracy include sensitivity and specificity. Although these measures are often considered fixed properties of a diagnostic test, in reality they are subject to multiple sources of variation such as the population case mix and the severity of the disease under study. Furthermore, when evaluating a new diagnostic test, it must be compared to a reference standard, although the latter is usually not perfect. In daily practice diagnostic tests are not used in isolation. Several issues will influence the interpretation of their results. First, clinicians have a prior assumption about the patient's chances of having the disease under investigation, based on the patient's characteristics, symptoms, and the disease prevalence in similar populations. Second, diagnostic tests are usually part of a diagnostic strategy. Therefore, it is not sufficient to determine the accuracy of a single test; one also needs to determine its additional value to the patient's diagnosis, treatment, or outcome as part of a diagnostic strategy.
authors.affiliation: Department of Medical Informatics, ERA-EDTA Registry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Karlijn J
authors.initials: KJ
authors.lastname: van Stralen
authors.affiliation: Department of Medical Informatics, ERA-EDTA Registry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Vianda S
authors.initials: VS
authors.lastname: Stel
authors.affiliation: Department of Clinical Epidemiology, Biostatistics, and Bioinformatics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Johannes B
authors.initials: JB
authors.lastname: Reitsma
authors.affiliation: Department of Medical Informatics, ERA-EDTA Registry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Friedo W
authors.initials: FW
authors.lastname: Dekker
authors.affiliation: Renal and Transplantation Unit, CNR-IBIM Clinical Epidemiology and Pathophysiology of Renal Disease and Hypertension, Ospedali Riuniti, Reggio Cal, Italy.
authors.forename: Carmine
authors.initials: C
authors.lastname: Zoccali
authors.affiliation: Department of Medical Informatics, ERA-EDTA Registry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: K.J.Jager@AMC.UVA.nl.
authors.forename: Kitty J
authors.initials: KJ
authors.lastname: Jager