Investigators developed two low-risk decision rules that predict which children with acute abdominal pain do not have appendicitis and can therefore be safely treated with observation: 

The prospective study was conducted in 601 patients between 3 and 18 years old who visited an emergency room with signs and symptoms that suggested appendicitis. Patients underwent diagnostic imaging or surgery, or both; some were discharged and others admitted for observation.  

After determining the ultimate diagnosis for each patient, investigators calculated the specificity and sensitivity of the decision rules and whether their application would, theoretically, have allowed patients to avoid computed tomography (CT) or surgery. They found that application of the first clinical rule would have reduced the use of CT by 23% and that application of the second rule would have reduced the use of CT by 20%. In addition, surgery could have been avoided in six patients whom both rules classified as being at low risk. (Those six patients had both a false-positive CT scan and a normal appendix on pathologic anlaysis.) On the other hand, the clinical decision rules misclassified as being at low risk four patients who turned out to have appendicitis but not a perforated appendix (Kharbanda AB et al: 