Diagnostic test evaluation and comparison

Positive and Negative Predictive Values for a test

	Sensitivity	Specificity

Prior probability of infection (prevalence)

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Use this to calculate the positive and negative predictive values for a test of known sensitivity and specificity for a range of prior probabilities of infection.

Inputs:

• Test unit sensitivity;
• Test unit specificity; and
• Prior probability of infection.

Outputs:

• Positive (PPV) and negative (NPV) predictive values for given inputs; and
• Table and plot of PPV and NPV for given sensitivity and specificity values and varying prior probability of infection.