Overview :

The specificity of a test is the number of true-negative test results divided by the number of all patients without the disease.

specificity =

= (d / (b + d))

where:

• d = true negatives

• (b + d) = false positives + true negatives = all people without disease

Comments:

• The better the sPecificity of the test, the fewer the false Positives.

• The specificity is the true negative rate.

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Goldman L. Chapter 10: Quantitative aspects of clinical reasoning. pages 43-48. IN: Isselbacher KJ, Braunwald E, et al. Harrison's Principles of Internal Medicine, Thirteenth Edition. McGraw-Hill. 1994.

Panzer RJ, Black ER, Griner PF. Interpretation of diagnostic tests and strategies for their use in quantitative decision making. pages 17-28. IN: Panzer RJ, Black ER, et al. Diagnostic Strategies for Common Medical Problems. American College of Physicians. 1991.

Speicher C, Smith JW Jr.. Choosing Effective Laboratory Tests. WB Saunders. 1983. pages 50-51, and 210