In medicine, an indication is a valid reason to use a certain test, medication, procedure, or surgery.[1] The opposite of indication is contraindication.[2]
In the United States, indications for medications are strictly regulated by the Food and Drug Administration (FDA), which includes them in the package insert under the phrase "Indications and Usage". Most countries and jurisdictions have a licensing body whose duty it is to determine whether to approve a drug for a specific indication, based on the relative safety of the drug and its efficacy for the particular usage being investigated. The EMA holds this responsibility for the whole of the European Union.
If a drug is prescribed or taken outstanding to its applied indications, such use is termed off-label.[3]
There are different classes of indication of drugs depending on validity of the benefit gained by the use of specific drug. As the consensus to use the drug increases its class of indication is improved.
Each test has its own indications and contraindications, but in a simplified fashion, how much a test is indicated for an individual depends largely on its net benefit for that individual, which largely depends on the absolute difference between pre- and posttest probability of conditions (such as diseases) that the test is expected to achieve. Additional factors that influence a decision whether a medical test should be performed or not include: cost of the test, time taken for the test or other practical or administrative aspects. The possible benefits of a diagnostic test may also be weighed against the costs of unnecessary tests and resulting unnecessary follow-up and possibly even unnecessary treatment of incidental findings.[4] Also, even if not beneficial for the individual being tested, the results may be useful for the establishment of statistics in order to improve health care for other individuals.