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

From: Conceptualization of category-oriented likelihood ratio: a useful tool for clinical diagnostic reasoning

  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 = 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 = 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 = 0 . 03 6 1 + 0 . 03 6 = 3%
  By regarding pre-test probability of neoplasm sub category, its probability can be revised as:
1. Pre-test odds = 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 = 0 . 00 9 1 + 0 . 00 9 = 0.8%