A clinical decision rule to identify children at low risk for appendicitis

Objective. Computed tomography (CT) has gained widespread acceptance in the evaluation of children with suspected appendicitis. Concern has been raised regarding the long-term effects of ionizing radiation. Other means of diagnosing appendicitis, such as clinical scores, are lacking in children. We sought to develop a clinical decision rule to predict which children with acute abdominal pain do not have appendicitis. Methods. Prospective cohort study was conducted of children and adolescents who aged 3 to 18 years, had signs and symptoms suspicious for appendicitis, and presented to the emergency department between April 2003 and July 2004. Standardized data-collection forms were completed on eligible patients. Two low-risk clinical decision rules were created and validated using logistic regression and recursive partitioning. The sensitivity, negative predictive value (NPV), and negative likelihood ratio of each clinical rule were compared. Results. A total of 601 patients were enrolled. Using logistic regression, we created a 6-part score that consisted of nausea ( 2 points), history of focal right lower quadrant pain ( 2 points), migration of pain ( 1 point), difficulty walking ( 1 point), rebound tenderness/pain with percussion ( 2 points), and absolute neutrophil count of > 6.75 x 10(3)/mu L ( 6 points). A score <= 5 had a sensitivity of 96.3% (95% confidence interval [CI]: 87.5-99.0), NPV of 95.6% ( 95% CI: 90.8-99.0), and negative likelihood ratio of .102 ( 95% CI: 0.026-0.405) in the validation set. Using recursive partitioning, a second low-risk decision rule was developed consisting of absolute neutrophil count of < 6.75 x 10(3)/mu L, absence of nausea, and absence of maximal tenderness in the right lower quadrant. This rule had a sensitivity of 98.1% ( 95% CI: 90.1-99.9), NPV of 97.5% ( 95% CI: 86.8-99.9), and negative likelihood ratio of 0.058 ( 95% CI: 0.008-0.411) in the validation set. Theoretical application of the low-risk rules would have resulted in a 20% reduction in CT. Conclusions. Our low-risk decision rules can predict accurately which children are at low risk for appendicitis and could be treated safely with careful observation rather than CT examination.