A diagnostic test is any kind of medical test performed to aid in the medical diagnosis|diagnosis or detection of disease. For example:
* to medical diagnosis|diagnose diseases, and preferably sub-classify it regarding, for example, severity and treatability
* to confirm that a person is free from disease
Companion diagnostics have also been developed to preselect patients for specific treatments based on their own biology. Such targeted therapy holds great promise in the treatment of diseases such as cancer.
A drug test can be a specific medical test to ascertain the presence of a certain drug in the body (for example, in drug addiction|drug addicts).