ABSTRACT
Likelihood ratios are helpful in determining how useful diagnostic tests will be. A likelihood ratio can predict how the result of a diagnostic test will transform the pre-test likelihood (i.e. the chance of having the disease, or in other words: the prevalence of the disease) to a post-test likelihood, i.e. the chance of having the disease knowing the test result There are two likelihood ratios:
• The positive likelihood ratio is the likelihood ratio that should be applied when the test result is positive (or abnormal).
