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INTERNSHIP SURVIVAL GUIDE
Disease
No disease
Positive test
True positive (TP)
A
False positive (FP)
B
All with positive test = A + B
Positive predictive value (PPV) = [A/(A + B)]
All with negative test = C + D
Negative predictive value (NPV) = [D/(C + D)]
Negative test
False negative (FN)
C
True negative (TN)
D
All with disease = A + C
Sensitivity = [A/(A + C)]
All without disease = B + D
Specificity = [D/(B + D)]
Figure 4-1.
Medical epidemiology.