The diagnosis of acute appendicitis (AA) sometimes is illusive and the accompanying clinical and laboratory manifestations cannot be used for definitive diagnosis. Objective: This study aimed to evaluate the diagnostic value of neutrophil/lymphocyte ratio (NLR) in detection of AA. Materials and Methods: This is a cross-sectional study that included a total of 80 adult patients with AA and 62 age- and gender-matched patients with abdominal pain due to causes other than AA. Three milliliter of peripheral blood were collected from each participant. The NLR was calculated by dividing the absolute neutrophil count by the absolute lymphocyte count. Receiver operating characteristic curve was used to assess the diagnostic value of NLR in detection of AA cases. Results: Mean NLR in AA patients was 7.18 ± 2.11 compared with 2.68 ± 1.08 in patients with abdominal pain due to causes other than AA with a highly significant difference. The area under the curve was 0.916 (95%confidence interval = 0.842–0.989), P < 0.001. The sensitivity and specificity of the test at NLR = 4.45 were 90% and 83%, respectively. Conclusions: NLR is an easy, inexpensive test that can be used for AA detection. This test is more sensitive and more specific than either total white blood cell or absolute neutrophil count
