S100A8/A9: A Potential New Diagnostic Aid for Acute Appendicitis

Objectives: Diagnosing acute appendicitis is a daunting clinical challenge, as there is no single test that reliably distinguishes acute appendicitis from other etiologies of acute abdominal pain. In this study, the authors examined whether circulating levels of S100A8/A9 could be useful as a marker to aid in the diagnosis of acute appendicitis. Methods: Plasma samples from emergency department (ED) patients with acute abdominal pain (n = 181) were tested using an immunoassay for S100A8/A9. Results: The sensitivity and specificity for S100A8/A9 in diagnosing acute appendicitis were estimated to be 93% (95% confidence interval [CI] = 81% to 97%) and 54% (95% CI = 45% to 62%), respectively. Negative predictive value (NPV) was 96% (95% CI = 89% to 99%), and positive predictive value (PPV) was 37% (95% CI = 28% to 47%). Performance characteristics of elevated white blood cell (WBC) count were also estimated: sensitivity 63% (95% CI = 47% to 76%), specificity 67% (95% CI = 59% to 75%), NPV 86% (95% CI = 78% to 91%), and PPV 36% (95% CI = 26% to 47%). Conclusions: This is the first report exploring the relationship between circulating S100A8/A9 and acute appendicitis and establishes proof of concept for this biomarker as a diagnostic test for acute appendicitis. Further studies are indicated to optimize the use of this biomarker, in conjunction with other established approaches. ACADEMIC EMERGENCY MEDICINE 2010; 17:333–336 © 2010 by the Society for Academic Emergency Medicine