# 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%