Can appendicitis occur without leukocytosis (elevated White Blood Cell (WBC) count)?

Appendicitis Can Occur Without Elevated White Blood Cell Count

Yes, appendicitis can definitely occur without an elevated white blood cell (WBC) count, as laboratory test results may be normal in the setting of appendicitis. 1

Understanding WBC Count in Appendicitis Diagnosis

• Although WBC count is frequently used in evaluating acute appendicitis, when used alone it is not a consistent predictor of the condition 1
• The negative likelihood ratio of an elevated WBC count (>10,000/mm³) for appendicitis is only 0.25, meaning a normal WBC count does not reliably exclude appendicitis 1
• Multiple studies have demonstrated that appendicitis can present with normal or even low WBC counts, particularly in certain patient populations 2, 3

Diagnostic Value of WBC Count

• An elevated WBC count (>10,000/mm³) has a positive likelihood ratio of only 2.47 for appendicitis, indicating limited diagnostic power 1
• The sensitivity of an elevated WBC count for appendicitis is approximately 67%, meaning about one-third of appendicitis cases may have normal WBC counts 4
• A case report documented perforated appendicitis presenting with leukopenia (WBC count of only 1800/μL), highlighting that even severe cases can occur without leukocytosis 2

Improving Diagnostic Accuracy

• Combining WBC count with other inflammatory markers significantly improves diagnostic accuracy:
  • The combination of WBC count and C-reactive protein (CRP) provides much better diagnostic value than either test alone 1, 5
  • Normal WBC count combined with normal CRP has a negative predictive value of 98.8% for appendicitis 5
  • Normal absolute neutrophil count (ANC) combined with normal CRP has shown 100% sensitivity and 100% negative predictive value in some studies 5

Age-Related Considerations

• The diagnostic value of WBC count varies by age group:
  • In toddlers (1-3.9 years), 4.8% with normal WBC counts still had appendicitis 4
  • In children (4-11.9 years), normal or low WBC count had a negative predictive value of 89.5% 4
  • In adolescents (12-19 years), 8.3% with normal WBC counts had appendicitis 4

Clinical Decision Making

• Clinical findings (signs and symptoms) should be used to risk-stratify patients with suspected appendicitis, rather than relying solely on laboratory values 1
• The Alvarado score, which combines symptoms, physical examination findings, and laboratory values, can help guide clinical decision-making but still has limitations 1
• Studies have shown that 8.4% of patients with appendicitis had low Alvarado scores (below 5), which would typically be considered low-risk 1

Imaging Considerations

• When laboratory findings are normal but clinical suspicion remains, imaging studies should be considered:
  • Abdominal ultrasound showing an appendiceal diameter of 6mm or larger has high sensitivity (98%) and specificity (98%) for appendicitis, regardless of WBC count 6
  • CT scanning may be appropriate even for patients with normal laboratory values when clinical suspicion exists 1

Key Pitfalls to Avoid

• Do not rule out appendicitis based solely on a normal WBC count, as this can lead to missed diagnoses 1, 2
• Recognize that appendicitis in certain populations (very young, elderly) may present atypically with normal laboratory values 1
• Remember that early appendicitis may not yet demonstrate laboratory abnormalities 1
• Accurate diagnosis ultimately depends on clinical history and physical examination findings, supported by laboratory and imaging studies 2