special subjects
Understanding Medical Tests and Test Results
Sequential Testing
Clinicians often do tests in sequence during many diagnostic evaluations. If the pre-test odds before sequential testing are known and the LR for each of the tests in sequence is known, post-test odds can be calculated using the following formula: Pre-test odds×LR1×LR2×LR3=post-test odds This method is limited by the important assumption that each of the tests is conditionally independent of each other. 