Background: Acute appendicitis (AA) is the first cause of emergency surgery. Leucine-Rich Alpha-2-Glycoprotein 1 (LRG1) has been shown to be a potential biomarker in cases of AA in children, but there are conflicting results for its use in adults. The objective of this study is to compare the mean plasma values of LRG1 in patients with acute abdomen with and without appendicitis Methods: This case-control study was conducted prospectively at the emergency room (ER) of Hospital de Clínicas de Porto Alegre, between March 1st, 2011 and December 31st, 2012. Patients with recente abdominal pain, aged 14-70 years who attended the ER were included in the study. Blood samples were drawn at the initial consultation. Those who were submitted to surgery and had a pathology report of AA were considered as cases. Those without a need of surgery and treated for other conditions, e.g., pelvic inflammatory disease, were considered as controls. Follow-up in controls was made up to 30 days. LRG1 plasma mean values were measured using ELISA kit and compared between groups. Results: A total of 28 participants, 14 cases with acute appendicitis and 14 controls, were included. The median (range) values of leucine-rich alpha-2-glycoprotein-1 level in the group with appendicitis and control group were 8.8 ng/ml (5.5 to 31) and 11 (4.6 to 108) ng/ml, respectively (Mann-Whitney test P=0.26). Conclusion: serum leucine-rich alpha-2-glycoprotein-1 levels were not useful in diagnosing Acute Appendicitis in patients with acute abdominal pain
