Most of the existing diagnostic scores have the weakness of being originally based on retrospective data of patients with appendicitis, a small number of patients, or paediatric patients. In retrospective studies, a potential systematic bias involves ignoring the number and outcome of non-operated patients presenting with clinical suspicion of appendicitis. In children, in comparison to adults, the diagnostic limit of leukocyte count and differential diagnosis of acute abdominal pain vary, and depend on age