Sensitivity and Specificity in Diagnosis


Sensitivityand Specificity in Diagnosis

Sensitivityand Specificity in Diagnosis

Sensitivityand specificity are widely used statistics that describe a diagnostictest. Sensitivity in diagnostic testing is the probability ofpositivity of the results in a diagnostic test. In this regard, amongthe patients that have been tested and have the disease, sensitivityreflects the probability of a positive test. For example, if abacterial rest to 20 people shows that 16 test positive, then thesensitivity of the test is 16/20 to give 80%. According to Goroll andMulley (2009), sensitivity evaluates the results of a diagnosis inorder to help in ruling out the disease. If a test is negative in ahighly sensitive diagnostic test, then the clinician can be certainthat the patient is not infected.

Specificityis diagnostic test is the proportion of the individuals being testedthat does not have the disease, and they get negative results (McGee,2012). For example, if an HIV tests in a population of 50 shows that45 of them are not infected, then the specificity of the test is45/50 to give 90%. Another good example of specificity would be themeasure of the people with HIV, but tested negative during theinitial test.

Theconcepts of sensitivity and specificity aid the selection of theresults by examining the outcomes of a test differently. Fletcheret al (2013) argues that thetwo concepts are useful because they consider the knowledge of thestatus of the patient in regard to the condition being tested. Whilesensitivity focuses on the people who test positive, the specificityis interested in the people who test negative. Therefore, they helpto analyze the results in regard to the statistics of the twooutcomes. Therefore, the two concepts aid in the interpretation oftest results.


Fletcher,R. et al (2013). ClinicalEpidemiology: The Essentials.Philadelphia:Lippincott Williams &amp Wilkins

Goroll,A., &amp Mulley, A.G. (2014). PrimaryCare Medicine: Office Evaluation and Management of the Adult Patient.Philadelphia:Lippincott Williams &amp Wilkins

McGee,S.R. (2012). Evidence-basedPhysical Diagnosis.NewYork:ElsevierHealth Sciences

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