Utility of Symptom Duration and C-Reactive Protein, White Blood Cell Count, and Absolute Neutrophil Count in the Evaluation of Pediatric Appendicitis

Background: Appendicitis is a common pediatric surgical emergency, and the diagnosis may be delayed or missed because of nonspecific findings in children. Not all patients with abdominal pain need to be imaged for appendicitis, and laboratory evaluation may improve diagnostic accuracy in this population. Objective: To determine if C-reactive protein (CRP) and symptom duration could be used to improve diagnosis of appendicitis compared with white blood cell count (WBC) and absolute neutrophil count (ANC). Methods: This was a retrospective chart review from June 2017 to 2019 at our tertiary academic children's hospital. A consecutive sample of all children <18 years of age being evaluated for appendicitis who had magnetic resonance imaging ordered were included. The diagnostic accuracy of WBC, ANC, and CRP were compared for patients with symptom duration ≤1 day compared with symptom duration for >1 day. Results: Five hundred thirty-nine patients were identified. The sensitivity and specificity of WBC (10,000 cells/μL) was 87.1% and 65.2%, respectively; ANC (7,500 cells/μL) was 86.5% and 70.8%, respectively; and CRP (0.5 mg/dL) were 73.7% and 58.1%, respectively. At >1 day of symptom duration, the specificity of WBC and ANC increased to 74.9% and 80.9%, respectively, and the sensitivity of CRP increased to 88.9%. Three patients with appendicitis (2.8%) had no laboratory abnormalities. Conclusions: No laboratory test studied has adequate characteristics to be used alone. CRP adds minimal sensitivity beyond WBC and ANC when symptoms are >1 day but with poor specificity, making it of limited utility.