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# Table 5 Calculation of post-test probability of categories using *category-oriented likelihood ratios* in approaching non-acute abdominal pain

According to table 3, post-test probability of organic diseases category in case 2 after negative answer about 5 key discriminatory questions in history taking can be calculated as: | |

1. | Pre-test odds = \frac{0.14}{1-0.14} = 0.16 |

2. | Post-test odds = 0.16 × 0.78 × 0.89 × 0.77 × 0.72 × 0.89 × 0.93 = 0.05 |

3. | Post-test probability = \frac{0.05}{1+0.05} = 4% |

Normal values of 3 key discriminatory clinical finding from table 4 again decrease the probability of organic category as: | |

1. | Post-test odds = 0.05 × 0.9 × 0.92 × 0.87 = 0.036 |

2. | Post-test probability = \frac{0.036}{1+0.036} = 3% |

By regarding pre-test probability of neoplasm sub category, its probability can be revised as: | |

1. | Pre-test odds = \frac{0.04}{1-0.04} = 0.041 |

2. | Post-test odds = 0.041 × 0.78 × 0.89 × 0.77 × 0.72 × 0.89 × 0.93 × 0.9 × 0.92 × 0.87 = 0.009 |

3. | Post-test probability = \frac{0.009}{1+0.009} = 0.8% |