How to Use an Article About a Diagnostic Test

PURPOSE: Urologists frequently confront diagnostic dilemmas, prompting them to select, perform and interpret additional diagnostic tests. Before applying a given diagnostic test the user should ascertain that the chosen test would indeed help decide whether the patient has a particular target condition. In this article in the Users' Guide to the Urological Literature series we illustrate the guiding principles of how to critically appraise a diagnostic test, interpret its results and apply its findings to the care of an individual patient. MATERIALS AND METHODS: The guiding principles of how to evaluate a diagnostic test are introduced in the setting of a clinical scenario. We propose a stepwise approach that addresses the question of whether the study results are likely to be valid, what the results are and whether these results would help urologists with the treatment of their individual patients. RESULTS: Some of the issues urologists should consider when assessing the validity of a diagnostic test study are how the authors assembled the study population, whether they used blinding to minimize bias and whether they used an appropriate reference standard in all patients to determine the presence or absence of the target disorder. Urologists should next evaluate the properties of the diagnostic test that indicate the direction and magnitude of change in the probability of disease for a particular test result. Finally, urologists should ask a series of questions to understand how the diagnostic test may impact the care of their patients. CONCLUSIONS: Application of the guides presented in this article will allow urologists to critically appraise studies of diagnostic tests. Determining the study validity, understanding the study results and assessing the applicability to patient care are 3 fundamental steps toward an evidence-based approach to choosing and interpreting diagnostic tests.