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%