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Diagnostic test evaluation and comparison

Positive and Negative Predictive Values for a test

  Sensitivity Specificity

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.


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


  • 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.