Gold standard (test)
In medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

 and statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....

, gold standard test refers to a diagnostic test
Medical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...

  or benchmark that is the best available under reasonable conditions. It does not have to be necessarily the best possible test for the condition in absolute terms. For example, in medicine, dealing with conditions that require an autopsy to have a perfect diagnosis, the gold standard test is normally less accurate than the autopsy.

Other times, gold standard is used to refer to the most accurate test possible without restrictions. The word is therefore ambiguous and its meaning should be deduced from the context in which it appears.

Gold standard in medicine

This can refer to diagnosing a disease process, or the criteria by which scientific evidence is evaluated. For example, in resuscitation research, the "gold standard" test of a medication or procedure is whether or not it leads to an increase in the number of neurologically intact survivors that walk out of the hospital. Other types of medical research might regard a significant decrease in 30-day mortality as the gold standard.

The AMA Style Guide prefers the phrase Criterion Standard instead of "gold standard", and many medical journals now mandate this usage in their instructions for contributors. For instance, Archives of biological Medicine and Rehabilitation specifies this usage.

A hypothetical ideal "gold standard" test has a sensitivity of 100% with respect to the presence of the disease (it identifies all individuals with a well defined disease process; it does not have any false-negative results) and a specificity of 100% (it does not falsely identify someone with a condition that does not have the condition; it does not have any false-positive results). In practice, there are sometimes no true "gold standard" tests. Sometimes they are called "perfect" and "alloyed" gold standard.

As new diagnostic methods become available, the "gold standard" test may change over time. For instance, for the diagnosis of aortic dissection
Aortic dissection
Aortic dissection occurs when a tear in the inner wall of the aorta causes blood to flow between the layers of the wall of the aorta and force the layers apart. The dissection typically extends anterograde, but can extend retrograde from the site of the intimal tear. Aortic dissection is a medical...

, the "gold standard" test used to be the aortogram, which had a sensitivity as low as 83% and a specificity as low as 87%. Since the advancements of magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...

, the magnetic resonance angiogram (MRA) has become the new "gold standard" test for aortic dissection, with a sensitivity of 95% and a specificity of 92%. Before widespread acceptance of any new test, the former test retains its status as the "gold standard."

Test calibration

Because tests can be incorrect (yielding a false-negative or a false-positive
Type I and type II errors
In statistical test theory the notion of statistical error is an integral part of hypothesis testing. The test requires an unambiguous statement of a null hypothesis, which usually corresponds to a default "state of nature", for example "this person is healthy", "this accused is not guilty" or...

), results should be interpreted in the context of the history, physical findings, and other test results in the individual being tested. It is within this context that the sensitivity and specificity of the "gold standard" test is determined.

When the gold standard is not a perfect one, its sensitivity and specificity
Sensitivity and specificity
Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...

 must be calibrated against more accurate tests or against the definition of the condition. This calibration is especially important when a perfect test is available only by autopsy.

Calibration errors can lead to misdiagnosis
Medical error
A medical error may be defined as a preventable adverse effect of care, whether or not it is evident or harmful to the patient. This might include an inaccurate or incomplete diagnosis or treatment of a disease, injury, syndrome, behavior, infection, or other ailment.-Definitions:As a general...


Gold standard ambiguity

Sometimes "Gold Standard test" refers to the best performing test available. In these cases, there is no other criterion against which it can be compared and it is equivalent to a definition. When referring to this meaning, gold standard tests are normally not performed at all. This is because the "gold standard" test may be difficult to perform or may be impossible to perform on a living person (i.e. the test is performed as part of an autopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...

or may take too long for the results of the test to be available to be clinically useful).

Other times, "Gold standard" does not refer to the best performing test available, but the best available under reasonable conditions. For example, in this sense, a MRI is the gold standard for brain tumour diagnosis, though it is not as good as a biopsy. In this case the sensitivity and specifity of the gold standard are not 100% and it is said to be an "imperfect gold standard" or "Alloyed gold standard"
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