Alvarado score is a practical score for the early diagnosis of acute appendicitis used as a clinical resource for diagnosing this disease. Acute appendicitis is the most common cause of an acute abdomen requiring surgery, with a lifetime risk of about 7 %. The Alvarado score was originally designed more than two decades ago, it enables risk stratification in patients presenting with abdominal pain, being a clinical prediction which rules and quantify the diagnosis of a target disorder based on findings or key symptoms and signs, thus having an independent diagnostic or prognostic value. Sensitivity and specificity of the score in acute appendicitis determines likehood of appendicitis based on symptoms, signs and laboratory data, and can be used to stratify patients with symptoms of suspected appendicitis. The aim of this study was to assess the diagnostic accuracy and calibration performance of the Alvarado score in a suspected acute appendicitis.