A new nuclear stress test modality is tested in a broad range of patients with suspected coronary artery disease. The patients' pre-test probability of having the disease is determined by their Framingham score. Their post-test probability is then calculated using the results of the new test, and the following curves are constructed.

The new test is most useful for diagnosing coronary artery disease in patients with which of the following pretest probabilities?

Question

A new nuclear stress test modality is tested in a broad range of patients with suspected coronary artery disease. The patients' pre-test probability of having the disease is determined by their Framingham score. Their post-test probability is then calculated using the results of the new test, and the following curves are constructed.

The new test is most useful for diagnosing coronary artery disease in patients with which of the following pretest probabilities?

Quizplus · Accepted Answer

11ec193a_9730_1171_853d_f1ad3f9f6808_MD0002_00 Test indication curves are graphical tools for determining whether a diagnostic test is indicated in a patient given a specific pre-test probability. These curves are created by entering the sensitivity and specificity of the test into Bayesian probability equations, which allows calculation of the post-test probability of disease for both positive and negative test results. These curves are most helpful when there is a certain threshold that the post-test probability must exceed before treatment is administered. The treatment threshold can be represented as a horizontal line drawn at the level of the corresponding post-test probability. The places where it intersects the test indication curves define testing thresholds and allow segregation of patients into 3 groups. The first group includes those in whom the chance of disease is sufficiently low that neither testing nor treatment is required (low pre-test probability). For patients in this no-test/no-treat group, the chance of the disease being present even after a positive test still falls below the threshold for treatment (Choices A and B). Likewise, in the no-test/treat group (high pretest probability), the chance of disease before the test is sufficiently high that even a negative result would not support a decision to withhold treatment (Choices D and E). Patients with a disease probability lying between these extremes belong in the test/treat-if-positive group. With a positive test result, the probability of disease becomes high enough to initiate treatment. The cutoffs between the no-test/no-treat, test/treat-if-positive, and no-test/treat groups can vary based on the treatment threshold that is selected. However, patients with the most intermediate pretest probabilities (ie, between 40%-60%) will generally benefit the most from being tested, as their disease probabilities will change the most after testing. Educational objective: Test indication curves facilitate the identification of 3 groups: those in whom the disease is assumed to be present and who are best treated empirically (no-test/treat group); at the other extreme, those who require neither testing nor treatment (no-test/no-treat); and those in the middle, for whom the test is indicated as the decision to treat would be based on the test result. __________

A New Nuclear Stress Test Modality Is Tested in a Broad