Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 57 12 2020 06 13 703 708 EN Seyed Isaac Hashemy Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. AND Department of Clinical Biochemistry, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Anvar Soleimani Department of Clinical Biochemistry, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Abolfazl Hekmat Shoar Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. Amin Lotfi Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. Arash Arianpour Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. Aghigh Ziaee Mehr Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran Mohammad Reza Motie Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. 2019 01 29 2020 04 24 Appendicitis is one of the main causes of acute abdominal surgery; however, the accurate diagnosis of appendicitis has remained uncertain. This study aimed to investigate the serum calprotectin as a diagnostic indicator for acute appendicitis. This prospective study was conducted on 79 patients suspected of acute appendicitis who underwent an appendectomy and 70 healthy volunteers. The correlation of serum calprotectin level and histopathological results was investigated. Screening performance characteristics of calprotectin (CP) were calculated on patients suspected with acute appendicitis. The mean serum calprotectin level in the patients was 0.791±0.148 mg/dl with a minimum of 0.567 mg/dl and a maximum of 1.26 mg/dl. The serum calprotectin ranged from 0.10 mg/dl to 0.50 mg/l in the healthy group. The AUC of CP was 0.58 (95% CI: 0.43-0.73). At a 0.72 mg/dl cutoff value, CP had 70% (95% CI: 58-82) sensitivity and 50% (95% CI: 39-61) specificity. According to the main finding of our study, the accuracy and sensitivity of serum CP in the detection of patients with acute appendicitis is good, and it seems that it can be used beside clinical symptoms for the diagnosis of acute appendicitis. https://acta.tums.ac.ir/index.php/acta/article/view/7723 https://acta.tums.ac.ir/index.php/acta/article/download/7723/5350