The positive likelihood ratio (LR+) is the probability of a positive test result in subjects with the condition, divided by the probability of a positive result in subjects without the condition, or sensitivity/(1–specificity). It indicates how much the probability of constipation changes from baseline when a symptom is present. On the other hand, the inverse of the negative likelihood ratio (1/LR-) is the probability of a negative test result when the condition is absent, divided by the probability of a negative test result when the condition is present, or specificity/(1-sensitivity). It indicates how much the probability of constipation changes when a symptom is absent.