Diagnostic Testing 101.1: The Importance of Sensitivity, Specificity and Diagnostic Test Accuracy

Multiple factors need to be considered in evaluating the diagnostic accuracy of a test including diagnostic validation and verification. Is the test testing what it is supposed to be testing for and are we doing it correctly?

Diagnostic accuracy of a test necessitates a reference standard, The reference standard can be the best available method for establishing the presence or absence of a condition (such as the throat culture for strep throat) or a combination of methods (imaging, neuropsychological testing, clinical exam, etc. in Alzheimer’s disease.

Any test that is going to be used as a basis for decisions that impact other human beings needs to be validated before it is introduced on the market. The literature needs to be reviewed critically and trials must be designed using objective evidence that validates the test is testing for what it purports to be and verifies the correct methodology of the test. Verification that the test is being collected, handled, stored, transported and processed correctly is requisite.

Cutoff levels, , cross-reactivity and myriad other issues need to be worked out prior to bringing a diagnostic test to market.

Disrupted Physician

To have striven, to have made an effort, to have been true to certain ideals — this alone is worth the struggle. We are here to add what we can to, not to get what we can from, life. – William Osler


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Diagnostic Medicine

Diagnostic medicine is the process of identifying the condition or disease that a patient has and  ruling out conditions or diseases the patient does not have through assessment of  the patient’s signs, symptoms, and results of various diagnostic tests.

Diagnostic Test Accuracy

Diagnostic test accuracy is simply the ability of the test to discriminate among alternative states of health (Zweig and Campbell, 1993).

If a test’s results do not differ between alternative states of health, then the test has insignificant accuracy; if the results do not overlap with other states of health then the test has perfect accuracy.  Most tests accuracies fall between these two extremes.

The intrinsic accuracy of…

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