What labs are recommended for a child presenting with abdominal pain?

Laboratory Tests for Children with Abdominal Pain

For children presenting with abdominal pain, white blood cell count with differential (including absolute neutrophil count) and C-reactive protein are strongly recommended as routine laboratory tests, particularly when appendicitis is suspected. 1

First-Line Laboratory Tests

• White blood cell (WBC) count with differential calculation of absolute neutrophil count (ANC) is a useful predictor of acute appendicitis in children 1
• C-reactive protein (CRP) level is a strong predictive factor for appendicitis, especially when ≥10 mg/L 1
• Leukocytosis ≥16,000/mL strongly suggests appendicitis in pediatric patients 1
• ANC >7,500/mL has been identified as a significant independent risk factor for appendicitis 1, 2
• Urinalysis should be included in the initial laboratory evaluation to rule out urinary tract infection as a cause of abdominal pain 3

Advanced Biomarker Panels

• 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 1
• Combining biomarker tests with clinical scoring systems improves diagnostic accuracy and helps determine the need for imaging 1
• Appendicitis Urinary Biomarker (AuB—leucine-rich alpha-2-glycoprotein) is promising for excluding appendicitis without blood sampling (negative predictive value 97.6%) 1

Laboratory Tests Based on Risk Stratification

Low Clinical Risk

• For children with low clinical risk of appendicitis based on scoring systems (like Pediatric Appendicitis Score or Alvarado), laboratory tests may not be necessary 1
• Other causes of abdominal pain should be sought in these cases 1

Intermediate/High Clinical Risk

• Complete laboratory workup including WBC with differential, CRP, and urinalysis is strongly recommended 1
• Human chorionic gonadotropin testing should be considered in adolescent females 3, 4
• Comprehensive metabolic profile may be appropriate for selected cases 3

Integration with Imaging

• Laboratory results should guide the decision for imaging studies 1
• Elevated inflammatory markers (WBC, ANC, CRP) in combination with clinical findings may indicate the need for ultrasound as the initial imaging modality 1
• Children with normal laboratory values but persistent symptoms may still require imaging based on clinical assessment 1

Diagnostic Accuracy Considerations

• No single laboratory test should be used in isolation to diagnose appendicitis 2
• The combination of clinical assessment tools with laboratory markers provides the highest diagnostic accuracy 2
• Laboratory tests should be interpreted in the context of the patient's age, as normal values and disease prevalence vary by age group 3, 4

Red Flags Requiring Urgent Evaluation

• Severe leukocytosis with left shift plus elevated CRP may indicate complicated appendicitis requiring urgent surgical consultation 1, 3
• Laboratory abnormalities accompanied by bilious vomiting, bloody diarrhea, absent bowel sounds, guarding, or rigidity warrant expedited evaluation 3, 4

The World Journal of Emergency Surgery strongly recommends routine laboratory tests and serum inflammatory biomarkers in children with suspected appendicitis, despite the evidence quality being rated as very low 1. These tests should be used in conjunction with clinical scoring systems and appropriate imaging to optimize diagnostic accuracy and guide management decisions.