Normal inflammatory markers in appendicitis: evidence from two independent cohort studies

Area of Science:

• Surgical pathology
• Diagnostic accuracy
• Inflammatory markers

Background:

• Acute appendicitis is a common surgical emergency.
• Normal inflammatory markers (WCC, CRP) have been suggested to indicate low risk.
• This study challenges the safety of discharging patients based solely on normal markers.

Purpose of the Study:

• To evaluate the reliability of white cell count (WCC), C-reactive protein (CRP), and neutrophil count (NC) in diagnosing appendicitis.
• To assess the risk of missing appendicitis in patients with normal inflammatory markers.

Main Methods:

• Retrospective cohort study in two UK district general hospitals.
• Analysis of sensitivity and specificity of CRP, WCC, and NC for appendicitis.
• Statistical analysis using Fisher's exact test and Kruskal-Wallace test.

Main Results:

• Appendicitis was present in patients with normal CRP, WCC, and NC.
• Combined marker sensitivity was high (92-94%), but specificity was moderate (60-64%).
• Elevated NC or CRP >35.5 mg/l predicted complicated appendicitis; combined markers differentiated appendix status.

Conclusions:

• Appendicitis can occur despite normal inflammatory markers.
• The strategy of discharging patients with normal WCC and CRP is potentially unsafe.
• Clinicians must maintain a high index of suspicion for appendicitis, even with normal inflammatory markers.