Prospective Validation of the Pediatric Appendicitis Score in a Canadian Pediatric Emergency Department

OBJECTIVES: Clinical scoring systems attempt to improve the diagnostic accuracy of pediatric appendicitis. The Pediatric Appendicitis Score (PAS) was the first score created specifically for children and showed excellent performance in the derivation study when administered by pediatric surgeons. The objective was to validate the score in a nonreferred population by emergency physicians (EPs). METHODS: A convenience sample of children, 4-18 years old presenting to a pediatric emergency department (ED) with abdominal pain of less than 3 days' duration and in whom the treating physician suspected appendicitis, was prospectively evaluated. Children who were nonverbal, had a previous appendectomy, or had chronic abdominal pathology were excluded. Score components (right lower quadrant and hop tenderness, anorexia, pyrexia, emesis, pain migration, leukocytosis, and neutrophilia) were collected on standardized forms by EPs who were blinded to the scoring system. Interobserver assessments were completed when possible. Appendicitis was defined as appendectomy with positive histology. Outcomes were ascertained by review of the pathology reports from the surgery specimens for children undergoing surgery and by telephone follow-up for children who were discharged home. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated. The overall performance of the score was assessed by a receiver operator characteristic (ROC) curve. RESULTS: Of the enrolled children who met inclusion criteria (n = 246), 83 (34%) had pathology-proven appendicitis. Using the single cut-point suggested in the derivation study (PAS 5) resulted in an unacceptably high number of false positives (37.6%). The score's performance improved when two cut-points were used. When children with a PAS of or=8 determined the need for appendectomy, the score's specificity was 95.1% with a PPV of 85.2%. Using this strategy, the negative appendectomy rate would have been 8.8%, the missed appendicitis rate would have been 2.4%, and 41% of imaging investigations would have been avoided. CONCLUSIONS: The PAS is a useful tool in the evaluation of children with possible appendicitis. Scores of or=8 help predict appendicitis. Patients with a PAS of 5-7 may need further radiologic evaluation.