Diagnosing Acute Appendicitis in Children with Neutrophil-Lymphocyte Ratio: A Cross-Sectional Study Running title: Diagnosing AA in Children with NLR

Purpose This study aimed to evaluate the value of neutrophil-to-lymphocyte ratio (NLR) in diagnosing AA in the pediatric population. Methods This retrospective cross-sectional study involved 200 pediatric patients aged between 0–14 years of both sexes, admitted as a case of acute appendicitis (AA). Data of patients retrieved from the hospital's patient administration system database. Normal appendex group (n = 100) included patients with abdominal pain without appendicitis. Uncomplicated AA group (n = 165) included patients with abdominal pain diagnosed with simple AA and treated with medical treatment or simple appendectomy. Complicated AA group (n = 35) included patients with recurrent or complicated appendicitis. Results White blood cells (WBCs), neutrophils and NLR were significantly higher in the uncomplicated and complicated appendicitis groups than the normal appendix group and in the complicated appendicitis group than the uncomplicated appendicitis group. In multivariate regression, WBCs and NLR were independent predictors for AA (P ≤ 0.001). NLR was an independent predictor for complicated appendicitis (P = 0.012). NLR can significantly predict AA and complicated appendicitis repectively at cut-off > 1.7 and > 10.1 with 74% and 68.57% sensitivity, and 69% and 56.98% specificity. Conclusions NLR is a valuable and cost-effective diagnostic marker for AA and complicated appendicitis in the pediatric population.