Predicting the Likelihood of Appendicitis Based on Clinical and Laboratory Findings

A meta-analysis of 24 studies looked at the use of clinical and laboratory predictors of appendicitis in terms of their predictive and discriminatory values [10]. Receiver Operator Curves (ROC) were calculated to assess discriminatory power. The ROC is the proportion of true positives (patients with appendicitis) against true negatives (patients without appendicitis) for each value of the test. A value of 0.5 shows no discrimination and a value of 1.0 shows complete discrimination.

Positive likelihood ratios (+LR) were calculated to describe predictive value of the findings. A+LR is the likelihood that a given test result would be present in a patient with appendicitis. A positive likelihood ratio of >1 suggests that the post-test probability of appendicitis is greater that the pre-test probability.

The two tables on the next page show the variables with the highest +LR and ROC values from the meta-analysis [10].