Test accuracy measure | Formula* | Definition |
---|---|---|

Sensitivity | a/(a+c) | Proportion of those with the target condition correctly identified as having the condition |

Specificity | d/(b+d) | Proportion of those without the target condition correctly identified as not having the condition |

Positive predictive value | a/(a+b) | Proportion of those with the target condition out of the test positives |

Negative predictive value | d/(c+d) | Proportion of those without the target condition out of the test negatives |

Positive likelihood ratio (LR^{+}) | Ratio of the proportion that tests positive among those with the target condition compared to the proportion that tests positive among those without the target condition | |

Negative likelihood ratio (LR^{–}) | Ratio of the proportion that tests negative among those with the target condition compared to the proportion that tests negative among those without the target condition | |

Diagnostic OR | ad/bc or LR^{+}/LR^{–} | Ratio of the odds of positivity in those who have the target condition relative to the odds of positivity in those without the condition |

*Expressed based on the notation used in table 1.