Tehran University of Medical Sciences Frontiers in Emergency Medicine 2717-3593 4 3 2020 01 07 e74 e74 Neda Karkeabadi Department of General Surgery, Poursina Medical & Educational Center, Guilan University of Medical Sciences, Rasht, Iran Seyed-Adel Maleknia Department of General Surgery, Poursina Medical & Educational Center, Guilan University of Medical Sciences, Rasht, Iran Moein Moghadam-Ahmadi Department of General Surgery, Poursina Medical & Educational Center, Guilan University of Medical Sciences, Rasht, Iran Sina Salimi Department of General Surgery, Poursina Medical & Educational Center, Guilan University of Medical Sciences, Rasht, Iran Hossein Torabi Department of General Surgery, Poursina Medical & Educational Center, Guilan University of Medical Sciences, Rasht, Iran Ehsan Kazemnezhad-Leili Department of Clinical Statistics, Poursina Medical & Educational Center, Guilan University of Medical Sciences, Rasht, Iran Mohammad-Nima Yadi Department of Emergency Medicine, Poursina Medical & Educational Center, Guilan University of Medical Sciences, Rasht, Iran 2019 07 22 2019 12 08 Introduction: Acute appendicitis is one of the most common emergencies of general surgery. Contrary to simple appendicitis, the complicated cases are associated with higher morbidity and mortality. Except for pathology, no accurate diagnostic test has been found to identify complicated cases.  Objective: Here in, we aim to evaluate the serum C-Reactive Protein (CRP) level in both acute simple and complicated appendicitis.  Methods: In this diagnostic accuracy study, 199 patients with acute appendicitis were enrolled. The serum CRP level was evaluated in patients. Post-operatively, the patients were divided into simple and complicated appendicitis based on histopathological examination. Eventually, analysis of the CRP level and type of appendicitis was performed.  Results: Fifty-three patients were categorized into complicated appendicitis and 146 patients into simple appendicitis. The median of CRP was significantly higher in the complicated group. Additionally, the optimal cutoff point was as follows: [65.0 (25.0) vs 25.0 (51.0); P-value< 0.001]. The optimal cutoff point for CRP was more than 42 with 81.1% sensitivity (95% CI: 68.0 to 90.6), and 67.8% specificity (95% CI: 59.6 to 75.3). The positive (PPV) and negative predictive values (NPV), based on the prevalence of complicated appendicitis (26.6%) for optimal cutoff point, were 47.8% (95% CI: 37.1 to 58.6) and 90.8% (95% CI: 83.8 to 95.5).  Conclusion: Our study revealed that evaluation of serum CRP levels could be useful and beneficial in the diagnosis of acute complicated appendicitis. https://fem.tums.ac.ir/index.php/fem/article/view/223 https://fem.tums.ac.ir/index.php/fem/article/download/223/256