If more than one test or finding is used for diagnosis, the final post-test probability can be calculated by combining the likelihood ratio for each test.


post-test odds =

= (pre-test odds) * (likelihood ratio for test 1) * (likelihood ratio for test 2) * .... * (likelihood ratio for test n)



• For valid results, tests must be conditionally independent of each other, where conditionally independent indicates that the results of the tests are not associated with each other.

• If conditionally dependent tests are used, then the calculated post-test probability will be over-estimated.


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