Table 2 Calculation of post-test probability using likelihood ratios

1.

Odds = $\frac{probability}{1-probability}$

2.

Post-test odds = pre-test odds × likelihood ratios

For example, according to table 1, post-test probability of uncomplicated UTI in case1 can be calculated as:

Pre-test odds = $\frac{0.12}{\left(1-0.12\right)}=0.13$

Post-test odds = 0.13 × 1.5 × 1.8 × 3.1 × 4 = 4.35

Post-test probability = $\frac{4.35}{\left(1+4.35\right)}=81\%$