
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/(1sensitivity). It
indicates how much the probability of constipation changes when a symptom is
absent. 