Likelihood ratios assess the probability or likelihood that the test result obtained would be expected in a person with the condition, compared to the probability or likelihood that the same result would be seen in a person without the condition (Deeks. 2001). The positive likelihood ratio 
expresses how many times more likely people with the condition are to receive a positive test result compared to those who do not have the condition, while the negative likelihood ratio 
expresses how likely it is that people with the condition will receive a negative test result compared to those who do not have the condition.
From the example presented in Table 9.2, 
The initial assessment of the likelihood of a disorder, that is the a priori probability, is modified by the results of the diagnostic test for a posteriori probability (the probability actually observed). A suggestion on the limited use of likelihood ratios is that their interpretation requires a calculator to convert between probabilities and odds of the disorder Los cocientes de probabilidad (CP) evalúan la probabilidad de que el resultado de la prueba obtenido sea el esperado en una persona con la enfermedad, en comparación con la probabilidad de que el mismo resultado se observe en una persona sin la enfermedad (Deeks. 2001).
La evaluación inicial de la probabilidad de un trastorno, es decir, la probabilidad a priori, se modifica con los resultados de la prueba diagnóstica para la probabilidad a posteriori (la probabilidad realmente observada). Una sugerencia sobre el uso limitado de los cocientes de probabilidad es que su interpretación requiere una calculadora para convertir entre probabilidades y probabilidades (odds) del trastorno (McGee. 2002).