Laboratory Tests for Diagnosing Appendicitis in Children

First-Line Laboratory Tests

The American College of Surgeons recommends white blood cell (WBC) count with differential calculation of absolute neutrophil count (ANC) as a useful predictor of acute appendicitis in children 1, 2
C-reactive protein (CRP) level is a strong predictive factor for appendicitis, especially when ≥10 mg/L, according to the World Journal of Emergency Surgery 1
Leukocytosis ≥16,000/mL strongly suggests appendicitis in pediatric patients, as reported by the World Journal of Emergency Surgery 1
ANC >7,500/mL has been identified as a significant independent risk factor for appendicitis by the World Journal of Emergency Surgery 2, 3

The APPY1 test panel (WBC, CRP, and myeloid-related protein 8/14) shows high sensitivity (97.8%) and negative predictive value (95.1%) for identifying children at low risk for appendicitis, according to the World Journal of Emergency Surgery 2
Combining biomarker tests with clinical scoring systems improves diagnostic accuracy and helps determine the need for imaging, as recommended by the World Journal of Emergency Surgery 1, 2
Appendicitis Urinary Biomarker (AuB—leucine-rich alpha-2-glycoprotein) is promising for excluding appendicitis without blood sampling (negative predictive value 97.6%), as reported by the World Journal of Emergency Surgery 1

For children with low clinical risk of appendicitis based on scoring systems, laboratory tests may not be necessary, according to the Journal of the American College of Radiology 4
Other causes of abdominal pain should be sought in these cases, as recommended by the Journal of the American College of Radiology 4

Complete laboratory workup including WBC with differential, CRP, is strongly recommended for children with intermediate or high clinical risk of appendicitis, according to the World Journal of Emergency Surgery and the Journal of the American College of Radiology 1, 4

Laboratory results should guide the decision for imaging studies, as recommended by the World Journal of Emergency Surgery and Clinical Infectious Diseases 2, 5
Elevated inflammatory markers (WBC, ANC, CRP) in combination with clinical findings may indicate the need for ultrasound as the initial imaging modality, according to Clinical Infectious Diseases 5, 6
Children with normal laboratory values but persistent symptoms may still require imaging based on clinical assessment, as recommended by the Journal of the American College of Radiology 4

The combination of clinical assessment tools with laboratory markers provides the highest diagnostic accuracy, as reported by the World Journal of Emergency Surgery 1, 2
No single laboratory test should be used in isolation to diagnose appendicitis, according to the World Journal of Emergency Surgery 1, 2

Severe leukocytosis with left shift plus elevated CRP may indicate complicated appendicitis requiring urgent surgical consultation, as recommended by the World Journal of Emergency Surgery 1