Clin Chem Lab Med 2017; 55(7): 1053–1059 Urszula Zielińska-Borkowska*, Naser Dib, Wiesław Tarnowski and Tomasz Skirecki Monitoring of procalcitonin but not interleukin-6 is useful for the early prediction of anastomotic leakage after colorectal surgery DOI 10.1515/cclm-2016-0736 Received August 17, 2016; accepted November 1, 2016; previously published online December 8, 2016 Abstract Background: Early recognition of patients who have devel- oped anastomotic leakage (AL) after colorectal surgery is crucial for the successful treatment of this complication. The aim of this study was to assess the usefulness of the assessment of procalcitonin (PCT) and interleukin-6 (IL-6) levels in the prognosis of AL. Methods: This observational study included 157 patients who underwent major elective colorectal surgery. The most common indications for surgery were cancer and inflam- matory bowel diseases. Serum samples were obtained directly before surgery (D0) and 1 day (D1) after surgery, and the relationships between the serum concentrations of PCT and IL-6 and development of AL were assessed. Results: In total, 10.2% of patients developed post-surgical infections due to AL. PCT levels on D1 were significantly higher in patients who developed AL [2.73 (1.40–4.62)] than in those who recovered without complications [0.2 (0.09– 0.44)]. The area under the ROC curve for PCT on D1 was 0.94, 95% CI (0.89–0.98). The sensitivity and specificity of the prediction of an infection were 87% and 87%, respec- tively, for PCT on D1, which was higher than 1.09 ng/mL. The increase in PCT concentration between D0 and D1 was significantly higher in patients with AL (p < 0.001). Patients who developed AL had higher concentrations of IL-6 on D1, but the difference was not significant (p = 0.28). Conclusions: This study confirms that surgical trauma increases serum PCT concentrations and that the con- centration of PCT on D1 can predict AL after colorectal surgery. However, IL-6 is not a good early marker for devel- oping AL. Keywords: anastomotic leakage; biomarker; interleukin-6; procalcitonin. Introduction Infections remain among the most serious complications of modern surgery. Despite the development of improved and less invasive techniques, any surgical interven- tion can result in infection, particularly gastrointestinal surgery [1]. Infections are one of the risk factors for anas- tomotic leakage (AL) [2]. At the same time, AL results in infections as well. Therefore, early diagnosis of postsurgi- cal infection is important. The high mortality of patients with AL (reaching 22%) makes it a life-threatening condi- tion that requires early diagnosis and treatment [3]. The clinical signs of surgical infection may only be present in the advanced phase, so a biomarker-guided approach is thought to be helpful. This is of particular importance in cases in which the clinical signs are ambiguous [4]. Elevated body temperature and leucocytosis are not sensi- tive indicators of septic complications [5]. Infections are especially concerning in patients with comorbidities that stimulate inflammatory responses and in those with mul- tifactorial risks of infection. To improve the early diagnosis of post-surgical infec- tions, a number of studies have investigated potential bio- markers [6]. Among them, procalcitonin (PCT) has been shown to be useful in many clinical settings, including the diagnosis of sepsis and early diagnosis of ventilator-associ- ated pneumonia [7–10]. Interleukin-6 (IL-6) is also consid- ered to be a candidate biomarker for infectious diseases [11]. PCT is a calcitonin prohormone composed of 116 peptide residues that has a mass of 14.5 kDa [12]. Bacte- rial infection causes a substantial increase in CALC-1 gene expression in all parenchymal tissues, with various cells in the system producing PCT. In the absence of infection, the PCT concentrations often remain below the detec- tion levels, but its concentration can increase as quickly as 2 h after exposure to a bacterial stimulus. The increase *Corresponding author: Urszula Zielińska-Borkowska, MD, PhD, Department of Anesthesiology and Intensive Care Medicine, Center of Postgraduate Medical Education, 231 Czerniakowska Street, Warsaw 00-416, Poland, E-mail: oit@szpital-orlowskiego.pl Naser Dib: Department of Oncological Surgery, European Health Centre, Otwock, Poland Wiesław Tarnowski: Department of General and Gastrointestinal Surgery, Centre of Postgraduate Medical Education, Warsaw, Poland Tomasz Skirecki: Department of Anesthesiology and Intensive Care Medicine, Centre of Postgraduate Medical Education, Warsaw, Poland