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Keywords:

  • diagnostic test;
  • evidence-based medicine;
  • urology

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. CONFLICT OF INTEREST
  5. REFERENCES

What's known on the subject? and What does the study add?

In our everyday practice as urologists, we often face diagnostic uncertainty that prompts us to perform a range of diagnostic tests to determine the probability that a patient has an underlying condition. Unfortunately, some diagnostic tests do not help us ‘rule in’ our ‘rule out’ a disease. These clinically unhelpful tests are not the best allocation of our healthcare system's resources.

This series will discuss the quality of evidence supporting the use of common diagnostic tests in urology. This discussion represents an important dimension of the decision-making process and appropriate interpretation of these tests. Through this series we hope to improve patient care by encouraging and informing readers to exercise selective application of these diagnostic tests to reduce the burden of rising and ultimately unsustainable healthcare costs.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. CONFLICT OF INTEREST
  5. REFERENCES

In our daily practice of urology, whether we find ourselves in the clinic, on the hospital ward or in the emergency room, we face diagnostic uncertainty. The need for additional clinical information prompts us to perform and order all kinds of diagnostic tests ranging from a physical examination, a microscopic urine analysis to a bone scan. Types of clinical questions that relate to diagnosis include ‘Does this boy have testicular torsion?’, ‘Does this woman have a UTI?’ or ‘Is this patient's back pain related to metastatic prostate cancer?’. Based on the clinical presentation, physical examination findings, and our clinical experience, we can usually assign a broad estimate of the probability that the patient has the suspected underlying condition. This probability might range from ‘very unlikely’ to ‘very likely’. Depending on the likelihood of the condition, and the implications for the patient's health if the condition is not appropriately diagnosed (and potentially treated), we commonly use diagnostic tests to refine our probability. Ideally, each of these tests will definitely ‘rule in’ or ‘rule out’ the condition of interest, be it torsion, a UTI, or symptomatic bone metastases, and provide clear guidance on how to best proceed in the care of the patient.

Unfortunately, medicine is rarely that simple. First, not all diagnostic tests are created equal; even in the best of circumstances some diagnostic tests lack the ability to shift our assumed probability of a given disease in a meaningful way, either in terms of ruling in or ruling out a disease. These tests are clinically unhelpful and should be avoided. Second, many tests are asymmetrical in their performance. For example, the test may have great value in excluding a condition (as characterised by high sensitivity) but little value in ruling in a condition (because of low specificity). In these cases, it is important to realise the differential value that a negative test result (in this case: helpful) or positive test result (in this case: not very helpful) may have and use the test selectively depending on the scenario. A third, and maybe most underappreciated issue, relates to the validity of the data that inform us about the diagnostic test. For treatments, we have guidelines to help critically appraise randomised controlled clinical trials [1]. Similarly, for diagnostic test studies, there is an accepted framework that helps a reader determine the extent we should believe and use a diagnostic test, in terms of the validity, impact, and applicability [2]. Important elements of this framework that relate to validity include whether the study investigators evaluated patients that truly faced diagnostic uncertainty, whether the new test was prospectively compared with an established reference standard, and lastly, whether the individuals determining the test outcomes were ‘blinded’ to the results of the reference standards or not [3]. The quality of evidence supporting the use of a diagnostic test, as determined by these and other criteria, represent an important dimension in the decision-making process of whether to use it in patient care.

Following in the footsteps of a highly successful set of review articles called ‘Evidence-Based Urology in Practice’[4], BJU International is launching a series that discusses the validity, potential impact, and applicability of commonly used diagnostic tests in urology. The purpose of this series is to help urologists better understand the benefits and limitations of available diagnostic tests. We hope that appropriate interpretation of these tests will improve patient care and selective application will reduce the burden of rising and ultimately unsustainable healthcare costs.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. CONFLICT OF INTEREST
  5. REFERENCES
  • 1
    Bajammal S, Dahm P, Scarpero HM, Orovan W, Bhandari M. How to use an article about therapy. J Urol 2008; 180: 190411
  • 2
    Schünemann HJ, Oxman AD, Brozek J et al. Grading quality of evidence and strength of recommendations for diagnostic tests and strategies. BMJ 2008; 336: 110610
  • 3
    Scales CD Jr, Dahm P, Sultan S, Campbell-Scherer D, Devereaux PJ. How to use an article about a diagnostic test. J Urol 2008; 180: 46976
  • 4
    Dahm P, for the Evidence-Based Urology Working Group. Introduction: evidence-based urology in practice. BJU Int 2010; 106 (Suppl. 2): 12