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Table 1 Calculating natural frequencies from estimates of sensitivity, specificity and prevalence

From: Understanding test accuracy research: a test consequence graphic

 

Target condition present

Target condition absent

Total

Test positive

TP = x × sens

FP = y − (y × spec)

TP + FP

Test negative

FN = x − (x × sens)

TN = y × spec

FN + TN

 

x = 1000 × p

y = 1000 − (1000 × p)

1000

  1. Sens sensitivity, spec specificity, p prevalence, TN true negative—test is negative and patient does not have target condition, FN false negative—test is negative but patient has target condition, TP true positive—test is positive and patient has target condition, FP false positive—test is positive but patient does not have target condition, x number of patients with target condition, y number of patients without target condition
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Diagnostic and Prognostic Research

ISSN: 2397-7523

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