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Overview :
Prevalence is all patients with disease divided by all
patients tested. This is also termed the
"prior probability."
prevalence =
= (a + c) / (a + b + c + d)
where:
• a + c = true positives + false negatives = all people with
disease
• (a + b + c +
d) = sum of (true positives, false positives, false negatives, true negatives)
= total population
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Braunwald E,
Isselbacher KJ, et al (editors). Harrison's
Principles of Internal Medicine, 11th edition. McGraw-Hill Book Publishers.
1987. page 7
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.
Speicher C,
Smith JW Jr.. Choosing Effective Laboratory Tests. WB Saunders. 1983. pages
50-51, and 210
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