Evidence-Based Practice: Diagnostic Evidence

Diagnostic Evidence: Understanding Diagnostic Tests and Statistics

Current Focus (Class 3 Fall 2025)

  • Diagnostic Evidence: Our current module focuses on understanding how diagnostic tests are used in the diagnostic process.

  • Key Learning Objectives:

    • Discuss the diagnostic process and the role of diagnostic tests.

    • Understand the quantitative aspects (numbers) related to diagnostic tests.

    • Develop skills to appraise diagnostic evidence critically.

  • Today's Topics:

    • Clinical Prediction Rules (CPRs) & Diagnostic Clusters: special types of diagnostic tests.

    • The mathematics and statistics used in diagnostic testing.

    • Strategies for reading diagnostic articles and tables effectively.

Previously in EBP II: The Diagnostic Process

  • Core Principle: Using diagnostic tests to adjust a pre-test probability (initial likelihood of a condition) to achieve a post-test probability (revised likelihood after testing) with the ultimate goal of reaching actionable certainty.

  • Probability Thresholds:

    • Test Threshold: The point below which further testing is no longer needed because the probability of the condition is too low to warrant it.

    • Treatment Threshold: The point above which the probability of the condition is high enough to justify initiating treatment without further testing.

    • The goal of testing is to move the probability from the