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

Abstract

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 and ANC may vary by age. The objective of this study was to investigate whether the diagnostic value of WBC 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 and ANC across 3 age groups: < 5 years, 5-11 years, 12-18 years of age. Diagnostic performance of WBC and ANC was then assessed at specific cut-points.

Results

2,133 patients with a median age of 10.9 years (IQR, 8-13.9) were studied. 41% had appendicitis. The area under-the-curve (AUC) for WBC was 0.69 [95% CI, 0.61-0.77] for patients < 5 years of age, 0.76 [95% CI, 0.73-0.79] for 5-11 years of age, and 0.83 [95% CI, 0.81, 0.86] for 12-18 years of age. The AUC's 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), 64% (12-18 years).

Conclusion

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

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