Acute appendicitis and plasma concentration of serotonin

The concentration of serotonin in platelet-poor plasma was measured with a radioenzymatic method in 31 patients prior to operation for suspected acute appendicitis. The serotonin determinations were made without knowledge of the peroperative or histologic findings. Appendicitis was found in 20 patients, nine of whom had elevated plasma serotonin level, giving 45% sensitivity for the test. Of the 11 patients with normal appendix, only one had increased plasma serotonin, giving 91% specificity. The predictive value of normal serotonin level was 48% and that of elevated serotonin level was 90%. No correlation was found between duration of appendicitis symptoms and plasma serotonin concentration. Other diseases did not influence the serotonin level.