Changes

Decisions made following diagnostic testing are usually dichotomous e.g. treat or do not treat the animal, therefore diagnostic tests are usually interpreted as dichotomous outcomes (diseased or non-diseased). In this case, if a diagnostic test is measuring a continuous outcome e.g. antibody titre then a cut-off for classifying animal’s as positive or negative must be selected. At whichever point the cut-off is selected there is usually some overlap between results i.e. some diseased animals will have the same value as non-diseased animals and hence, there will be false-positive and false-negative results.

Decisions made following diagnostic testing are usually dichotomous e.g. treat or do not treat the animal, therefore diagnostic tests are usually interpreted as dichotomous outcomes (diseased or non-diseased). In this case, if a diagnostic test is measuring a continuous outcome e.g. antibody titre then a cut-off for classifying animal’s as positive or negative must be selected. At whichever point the cut-off is selected there is usually some overlap between results i.e. some diseased animals will have the same value as non-diseased animals and hence, there will be false-positive and false-negative results.

[[File:testresults.jpg]]

[[File:Diagnostic test results.jpg]]

===Post-test probability===

===Post-test probability===