A prospective clinical trial evaluating urinary 5-hydroxiyindoleacetic acid levels in the diagnosis of acture appendicitis

Background: To improve the diagnostic accuracy of identifying acute appendicitis, imaging modalities, such as ultrasound and the computed tomography scan, are used in combination with the history and physical examination. There is no reliable single laboratory marker to assist with this diagnosis. During inflammation, enterochromaffin cells in the appendix secrete serotonin, and 5-hydroxyindoleacetic acid (5-HIAA), a serotonin metabolite excreted in urine, has been found to be elevated in patients presenting with acute appendicitis. Objective: The aim of this study was to measure the urinary 5-HIAA concentrations of patients presenting with symptoms of acute appendicitis to determine the sensitivity and specificity of urinary 5-HIAA levels for diagnosing acute appendicitis. Methods: 5-HIAA was quantitatively measured by high-performance liquid chromatography in the spot urine of 100 healthy individuals, aged 18 to 70 years, who presented to the emergency medicine department with a clinical picture of acute appendicitis. Urine concentration results were correlated to the gold standard of histopathologic reports of removed appendices. The sensitivity, specificity, and their 95% confidence intervals were derived. Results: Of the 100 patients presenting with symptoms consistent with acute appendicitis, 72 had appendectomies and 2 had cholecystectomies. The remaining 26 patients were discharged after hospital observation. A total of 64 patients were found to have appendicitis: 52 had acute appendicitis, whereas 12 had perforated and/or gangrenous (nonacute) appendices. The acute appendicitis group had a mean urinary 5-HIAA level of 19.31 mu mol/L, slightly lower than the 23.10 mu mol/L of the patients with gangrenous/perforated appendicitis. The group without appendicitis had a urinary 5-HIAA value of 17.27 mu mol/L. Using the lowest of previously reported cutoffs, we calculated the sensitivity and specificity of this test for acute appendicitis as 63% and 33%, respectively. Conclusion: Urinary 5-HIAA level is not a good diagnostic tool for determining acute appendicitis. (c) 2008 Elsevier Inc. All rights reserved.