You are welcome to keep this page and use the calculator off-line. Any comments are welcome. E-mail to me at DJRHutchon@Postmaster.co.uk

specificity = truenegatives/diseasenegatives [D/(B+D)]

LR+ = Sensitivity/(1-Specificity)

LR- = (1- Sensitivity)/Specificity

PPV =

NPV =

Accuracy =

Prevalence =

Pretest odds + =

Post-test probability + =

TPFN ratio =

DBFind 10,000 =

Sensitivity | Chance of having a positive test in patients with the test condition |

Specificity | Chance of having a negative test in patients without the condition |

LR+ve | Ratio of probability that patient with test condition has a positive test result to the probability that a patient without the condition has a negative test result |

LR-ve | Ratio of probability that patient with test condition has a negative test result to the parbability that a patient without the condition has a negative test result |

PPV | Chance of having test condition given a negative test result |

NPV | Chance of not having test condition given a negative test result |

Accuracy | The proportion of all tests that are correct |

Specificity | Chance of having a negative test in patients without the condition |

Prevalaence | True positives plus false negatives for the test condition as proportion of population |

Pre-test odds/probability | The odds/probability of the condition (prevalaence) in the whole community |

TPFN ration | The proportion of true positives to false negatives for the test condition |

DBFind 10,000 | The number of false negative cases in a database od 10,000 patients |