Can a Negative C-Reactive Protein Rule out Appendicitis?

Abstract

Background: Acute appendicitis is one of the commonest causes of acute abdomen. Several studies have looked at the role of C-reactive protein (CRP) and white cell count (WCC) in diagnosing acute appendicitis with varying results but there is a scarcity of such data in the U.A.E. The aim of this study was to determine the sensitivity and specificity of CRP, WCC and neutrophils count in the diagnosis of acute appendicitis. Methods: The study was carried out between December 2011 and December 2012. This was a prospectively conducted, retrospectively analyzed study. 535 patients underwent appendicectomy during the study period (418 laparoscopic and 117 open appendicectomies). Two hundred and forty nine patients were eligible for inclusion in the final analysis. The patients preoperative CRP, WCC and Neutrophils count were measured and compared to the histopathology of the appendix which was grouped into either positive or negative for appendicitis. Results: Out of 249 patients, 198 (79.5%) were male and 51 (20.5%) were female. The sensitivity and specificity of CRP were 77.31% (CI 71.74%-82.88%) and 51.51% (CI 34.54%-68.48%) respectively. Leukocytosis (WCC ≥12×109/L) had a sensitivity of 73.14% (CI 67.26%-79.02%) and a specificity of 51.51 %( CI 34.54%-68.48%), whereas a left shift (neutrophils count ≥ 80%) showed 66.66% (CI 60.47% - 72.85%) sensitivity and 75.75 % (CI 61.23%-90.27%) specificity Conclusion: In this study CRP, WCC and neutrophils count showed medium sensitivity and specificity for the histopathological diagnosis of acute appendicitis. This is consistent with other studies and with the wide range of sensitivity and specificity in published literature. Therefore, these tests should always be considered in the light of the clinical context whilst also judiciously utilizing other available resources such as radiological studies.