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

OBJECTIVES Acute appendicitis is a common surgical condition which can lead to severe complications. Recent work suggested that patients experiencing right lower abdominal pain, with normal white cell count (WCC) and C-reactive protein (CRP) are unlikely to have acute appendicitis and can be discharged. We present two independent data-sets that suggest that this strategy may not be risk-free. DESIGN Retrospective cohort study of consecutive patients from two district general hospitals. Sensitivity and specificity of CRP, WCC and neutrophil count (NC) in predicting appendicitis were calculated. Markers were analysed using Fisher's exact test and Kruskul-Wallace test. SETTING Two district general hospitals in the UK. PARTICIPANTS Patients undergoing appendicectomy for suspected appendicitis. MAIN OUTCOME MEASURES Inflammatory markers and appendix histology. RESULTS A total of 297 patients were included. Appendicitis occurred in four patients with normal CRP, WCC and NC in centre A and 13 patients in centre B. The sensitivity of all three markers combined was 94% (centre A) and 92% (centre B). The specificity was 60% (centre A) and 64% (centre B). No single marker could differentiate uncomplicated and complicated appendicitis, but a raised NC or a CRP >35.5 mg/l predicted complicated appendicitis. CRP, WCC and NC combined differentiated between patients with a normal appendix, uncomplicated appendicitis and complicated appendicitis. CONCLUSIONS Appendicitis in the presence of normal inflammatory markers is not uncommon. We disagree with the view of Sengupta et al. who suggest that patients with normal WCC and CRP are unlikely to have appendicitis, and recommend that clinicians be wary of normal inflammatory markers in patients with a high clinical suspicion of appendicitis.