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Division of General Internal Medicine

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Division of General Internal Medicine

Short Courses: 2x2 and Stratum Specific Likelihood Ratio Approaches to Interpreting Diagnostic Tests: How Different Are They?

MDM Short Course #8
2:00 - 5:30, Friday October 21, 2005

Course Description:

The 2x2 approach to interpreting diagnostic tests (which depends upon selection of the optimal 2x2 table, and in which a particular test result can lower one's prior for some patients and raise one's prior for others) appears to differ from the stratum specific likelihood ratio approach (in which a particular test result has a unique and unchanging likelihood ration). Yet both approaches derive from information theory, and in the "one test-and-done" approach to use of diagnostic tests, they yield the same treatment recommendations.

In this class, we introduce the two approaches plus the underlying treatment threshold (i.e., at the end of any testing sequence, the posterior probability above which one should treat and below which one should withhold treatment); show how the two approaches are linked through this treatment threshold; indicate cases where they lead to the same treatment recommendations and where they can lead to different treatment recommendations. We also discuss how these two conceptualizations affect choices among tests. We describe choice procedures when one (inappropriately) seeks to maximize the area under the ROC curve and when one (more appropriately) seeks to minimize the costs of mistakes. The course format is primarily didactic.

  • Henry Glick, PhD, University of Pennsylvania

  • Seema Sonnad, PhD, University of Pennsylvania