Gold standard (science)

Gold standard, or sometimes golden standard, refers to the best possible test, most commonly used in medicine to refer to a test for a condition or disease. A gold standard medical test is not necessarily perfect, but one that is recognised as good enough so that all other tests can be compared to it. This type of evidence is used to evaluate new methods of diagnosing disease as often the "gold standard" test may have the potential for complications, or is expensive or time consuming.

Examples
For example, the gold standard for diagnosing pulmonary embolism (PE) is the, in which dye is injected into the bloodstream and X-rays are taken of the arteries in the lungs. Because this is an invasive test, other methods of diagnosing the disease are desirable. Computed tomography (CT) scanning is an increasingly common method used to diagnose PE. To know how accurate it is, it must be compared to a test that is known to be good. Angiography is presumed to be nearly 100% sensitive and specific, and then CT can be compared to it, and its accuracy calculated.

A gold standard test, if expensive or invasive, can also be used in conjunction with a less sensitive/specific test. Where positive results from the more routine test lead to the invasive one in order to weed out false positives. However, these must be carefully weighed against the number of false negatives the tests also produce.

A blood draw for prostate-specific antigen (PSA) has controversially been used to screen for potential prostate cancer. Where high PSA levels in the test then trigger a more invasive, gold standard test: a biopsy. However, a study published in the New England Journal of Medicine concluded that PSA screening did not result in significantly lower prostate cancer mortality while potentially exposing healthy men to unnecessary post-PSA-test tests and treatment.