AIM To assess the accuracy of serum procalcitionin(PCT)as a diagnostic marker in verifying upper and lower gastrointestinal perforation(GIP).METHODS This retrospective study included 46 patients from the surgical intensive care unit(ICU)of the Second Affiliated Hospital of Harbin Medical University who were confirmed to have GIP between June 2013 and December 2016.Demographic and clinical patient data were recorded on admission to ICU.Patients were divided into upper(n=19)and lower(n=27)GIP groups according to the perforation site(above or below Treitz ligament).PCT and WBC count was obtained before laparotomy and then compared between groups.Meanwhile,the diagnostic accuracy of PCT was analyzed.RESULTS Patients with lower GIP exhibited significantly higher APACHE II score,SOFA score and serum PCT level than patients with upper GIP(P=0.017,0.004,and0.001,respectively).There was a significant positive correlation between serum PCT level and APACHE II score or SOFA score(r=0.715 and r=0.611,respectively),while there was a significant negative correlation between serum PCT level and prognosis(r=-0.414).WBC count was not significantly different between the two groups,and WBC count showed no significant correlation with serum PCT level,APACHE II score,SOFA score or prognosis.The area under the receiver operating characteristic curve of PCT level to distinguish upper or lower GIP was 0.778.Patients with a serum PCT level above 17.94 ng/d L had a high likelihood of lower GIP,with a sensitivity of 100%and a specificity of 42.1%.CONCLUSION Serum PCT level is a reliable and accurate diagnostic marker in identifying upper or lower GIP before laparotomy. AIM To assess the accuracy of serum procalcitionin (PCT) as a diagnostic marker in verifying upper and lower gastrointestinal perforation (GIP) .METHODS This retrospective study included 46 patients from the surgical intensive care unit (ICU) of the Second Affiliated Hospital of Harbin Medical University who were confirmed to have GIP between June 2013 and December 2016. Demographic and clinical patient data were recorded on admission to ICU. Patients were divided into upper (n = 19) and lower (n = 27) GIP groups according to the perforation site (above or below Treitz ligament) .PCT and WBC count was obtained before laparotomy and then compared between groups. Meanwhile, the diagnostic accuracy of PCT was analyzed.RESULTS Patients with lower GIP exhibited significantly higher APACHE II score, SOFA score and serum PCT level than patients with upper GIP (P = 0.017, 0.004, and 0.001, respectively). There was a significant positive correlation between serum PCT level and APACHE II score or SOFA score (r = 0.715 and r = 0. 611, respectively), while there was a significant negative correlation between serum PCT level and prognosis (r = -0.414) .WBC count was not significantly different between the two groups, and WBC count showed no significant correlation with serum PCT level, APACHE II score, SOFA score or prognosis. The area under the receiver operating characteristic curve of PCT level to distinguish upper or lower GIP was 0.778.Patients with a serum PCT level above 17.94 ng / d L had a high likelihood of lower GIP, with a sensitivity of 100% and a specificity of 42.1% .CONCLUSION Serum PCT level is a reliable and accurate diagnostic marker found in upper or lower GIP before laparotomy.