Admission Levels of Serum Amyloid A and Procalcitonin are More Predictive of the Diagnosis of Acute Appendicitis Compared With C-reactive Protein

Background: Acute appendicitis is the commonest surgical emergency, but its diagnosis can be elusive with a negative appendicectomy rate of 20%. The aims of this study were to investigate the potential value of the markers of acute inflammation, serum amyloid A (SAA), and serum procalcitonin (ProCT), in the diagnosis of acute appendicitis in adults and to compare that with the commonly used serum C-reactive protein (CRP). Methods: Adult patients presenting with acute right lower abdominal pain and a clinical suspicion of acute appendicitis were included. Blood samples were obtained within 6 hours of admission for rapid serum CRP assay and for end-of-recruitment batch analysis of SAA and serum ProCT concentrations. Results: A total of 147 patients (81 males) with a mean (+/- SD) age of 36 (+/- 17) years were recruited. Appendicitis was confirmed histologically in 61 of 72 patients (84.7%) who underwent appendicectomy. A post hoc analysis revealed a diagnostic sensitivity and specificity for SAA of 92% and 72%, ProCT of 85% and 74%, and CRP of 75% and 72%, respectively. The receiver operator characteristics for the area under the curves showed that SAA (P = 0.011) and ProCT (P = 0.037) significantly exceeded CRP in the prediction of acute appendicitis on admission. Conclusions: The measurement of SAA and serum ProCT on admission in patients with clinically suspected acute appendicitis seems to outperform serum CRP in aiding that diagnosis.