Analysis of Diagnostic Accuracy Measures

plot

PPV

NPV

OR

LR+

LR-

versus

sensitivity

specificity

prevalence of disease

prevalence

0.05

healthy population

mean

0

standard deviation

1

diseased population

mean

3.67

standard deviation

1

0.2

0.4

0.6

0.8

1.0

specificity

2

4

6

8

10

12

LR+

LR+ curve

This Demonstration shows plots of various accuracy measures for diagnostic tests on normally distributed healthy and diseased populations. This is done for differing prevalence of the disease, taking into account mean and standard deviations of the populations. The mean and standard deviations are expressed in arbitrary units. The measures considered are the positive prognostic value ("PPV"), the negative prognostic value ("NPV"), the (diagnostic) odds ratio ("OR"), the likelihood ratio for a positive result ("LR+"), and the likelihood ratio for a negative result ("LR-"). The measures are plotted against the sensitivity or the specificity of the test, which can be selected by clicking the respective button.