The Influence of Age on the Diagnostic Performance of White Blood Cell Count and Absolute Neutrophil Count in Suspected Pediatric Appendicitis.

OBJECTIVE: White blood cell (WBC) count and absolute neutrophil count (ANC) are a standard part of the evaluation of suspected appendicitis. Specific threshold values are utilized in clinical pathways, but the discriminatory value of WBC count and ANC may vary by age. The objective of this study was to investigate whether the diagnostic value of WBC count and ANC varies across age groups and whether diagnostic thresholds should be age-adjusted.

METHODS: This is a multicenter prospective observational study of patients aged 3-18 years who were evaluated for appendicitis. Receiver operator characteristic curves were developed to assess overall discriminative power of WBC count and ANC across three age groups: <5, 5-11, and 12-18 years of age. Diagnostic performance of WBC count and ANC was then assessed at specific cut-points.

RESULTS: A total of 2,133 patients with a median age of 10.9 years (interquartile range = 8.0-13.9 years) were studied. Forty-one percent had appendicitis. The area under the curve (AUC) for WBC count was 0.69 (95% confidence interval [CI] = 0.61 to 0.77) for patients < 5 years of age, 0.76 (95% CI = 0.73 to 0.79) for 5-11 years of age, and 0.83 (95% CI = 0.81 to 0.86) for 12-18 years of age. The AUCs for ANC across age groups mirrored WBC performance. At a commonly utilized WBC cut-point of 10,000/mm3 , the sensitivity decreased with increasing age: 95% (<5 years), 91% (5-11 years), and 89% (12-18 years) whereas specificity increased by age: 36% (<5 years), 49% (5-12 years), and 64% (12-18 years).

CONCLUSION: WBC count and ANC had better diagnostic performance with increasing age. Age-adjusted values of WBC count or ANC should be considered in diagnostic strategies for suspected pediatric appendicitis.