Understanding Diagnostic Tests-Series-What is Normal?

The field of Radiology and Imaging involves the routine use of a lot of imaging based diagnostic tests. The science that drives evidence based diagnoses and patient centered medicine also extends to image based diagnostic tests.

As a radiology and imaging specialized clinician, our primary concerns include

  • What test (s) should I choose for each patient?
  • If I have to use multiple tests, what should be the order of tests? Which test should I use first?
  • How do I interpret the results of the test? What measures should I consider when I report normal or abnormal states?
  • What should I communicate to the “test-ordering” physician?
  • How do I evaluate new diagnostic tests? Can I be sure they are reliable and valid?

We will try to address some of these concerns in a series that aims to better understand the diagnostic test environment.

Please note that we will restrict the material (at this stage) to a discussion that aims to help you translate diagnostic tests into clinical action.  

We will not get into great detail now (we will briefly touch upon these) regarding the calculation or estimation as these are taught as part of the medical curriculum level and are freely available on the net. Our focus will be on transferring that knowledge into routine clinical practice.


The series will explore

  • What is Normal in the context of a diagnostic test?
  • Diagnostic Test Terminology- What do they mean, application and limitations
    • Characteristics of a test
      • Sensitivity of a test
      • Specificity of a test
    • Applying the test Results to a clinical setting
      • Positive Predictive Values
      • Negative Predictive Values
    • Applying the test results to a clinical setting-moving further ahead
      • Pre-test Probability
      • Positive Likelihood Ratio
      • Negative Likelihood Ratio
      • Post-Test Probabilityv
      • Making a clinical decision
    • Discriminatory ability of test
      • Area under ROC curves

Anticipated Outcomes

  • A better understanding of the science behind diagnostic tests
  • A better understanding of the clinical applications of diagnostic test results
  • An improved ability to critically evaluate the diagnostic test literature including newer tests
  • An improved ability to design your own studies to evaluate diagnostic tests
  • A better understanding of limitations and how to adapt them for clinical use

View the first part of the series

A Presentation on “What is Normal in the context of a diagnostic test”