What is the diagnostic utility of White Blood Cells (WBCs) in pediatric appendicitis?

From the Guidelines

White blood cell (WBC) count is a useful but imperfect diagnostic tool for pediatric appendicitis, and its utility is enhanced when combined with other clinical findings and laboratory markers like C-reactive protein, as suggested by the 2020 update of the WSES Jerusalem guidelines 1. An elevated WBC count (typically above 10,000-12,000 cells/μL) with neutrophilia (increased neutrophil percentage) can support the diagnosis of appendicitis in children with suspicious clinical presentations. However, WBC count alone is insufficient for diagnosis as it lacks specificity - approximately 70-90% of children with appendicitis have leukocytosis, but many other conditions can also cause elevated WBCs. Some key points to consider when using WBC count in the diagnosis of pediatric appendicitis include:

• Serial WBC measurements showing a rising trend may be more informative than a single value.
• Very high WBC counts (>15,000-20,000 cells/μL) may suggest perforation or advanced disease.
• Normal WBC counts don't exclude appendicitis, as 10-30% of children with confirmed appendicitis may have normal counts.
• The use of clinical scores, such as the Pediatric Appendicitis Score (PAS) and the Alvarado score, can help in the diagnosis of appendicitis in children, but they should be used in combination with laboratory tests and imaging studies 1.
• The 2020 update of the WSES Jerusalem guidelines recommends the use of clinical scores to exclude acute appendicitis and identify intermediate-risk patients needing imaging diagnostics, and suggests that WBC count, differential with the calculation of the absolute neutrophil count, and CRP are useful lab tests in predicting acute appendicitis in children 1. Therefore, while WBC count serves as a helpful adjunct in the diagnostic workup, clinical assessment and imaging studies (ultrasound or CT) remain essential for accurate diagnosis of pediatric appendicitis.

From the Research

Utility of WBCs in Diagnosis of Appendicitis in Pediatrics

• The diagnostic value of white blood cell count (WBC) in pediatric appendicitis has been investigated in several studies 2, 3, 4, 5, 6.
• Elevated WBC count alone had a sensitivity of 0.6 in diagnosing appendicitis in children, while the combination of elevated WBC count and C-reactive protein (CRP) had a sensitivity of 0.98 2.
• The sensitivity of WBC count in diagnosing complicated appendicitis was 95.2%, making it a useful marker for diagnosis 3.
• High WBC counts and left shift were independently associated with appendicitis in children, with a sensitivity of 80% and specificity of 79% when combined 4.
• The diagnostic performance of WBC count varied across age groups, with better performance in older children 6.
• Age-adjusted values of WBC count should be considered in diagnostic strategies for suspected pediatric appendicitis 6.

WBC Count and Age

• The sensitivity of WBC count decreased with increasing age, while specificity increased 6.
• In children under 5 years, the sensitivity of WBC count was 95%, while in children 12-18 years, the sensitivity was 89% 6.
• The area under the curve (AUC) for WBC count was lower in younger children, indicating poorer diagnostic performance 6.

Combination of WBC Count and Other Markers

• The combination of WBC count and CRP had a higher sensitivity than WBC count alone in diagnosing appendicitis 2.
• The combination of WBC count and left shift had a higher sensitivity and specificity than WBC count alone in diagnosing appendicitis 4.
• The use of platelet indices, such as mean platelet volume/platelet count (MPV/PC) ratio, may also be useful in diagnosing pediatric appendicitis 5.