Diagnostic value of procalcitonin in distinguishing Gram-negative bacterial blood stream infection from Gram-positive bacterial infection in early stage of sepsis

Abstract

Objective To investigate the diagnostic values of procalcitonin(PCT), high sensitive C-reactive protein(hs-CRP), white blood cell(WBC) and percentage of neutrocyte(NEU%) in Gram-negative and Gram-positive bacterial blood stream infection in early stage of sepsis in order to investigate the correlation between PCT and APACHEⅡ score as well as between PCT and SOFA score, and the prognostic value in assessment of Gram-negative and Gram-positive bacterial blood stream infection. Methods Clinical data of patients admitted to ICU from January 2012 through December 2014 were retrospectively analyzed. A total of 124 sepsis patients with blood stream infection were checked with PCT, hs-CRP, WBC and NEU% tests, and APACHEⅡ score and SOFA score were calculated. The differences in APACHEⅡ score and SOFA score were compared between Gram-negative group (n=41) and Gram-positive group (n=83). The correlation between PCT and APACHEⅡscore as well as between PCT and SOFA score was analyzed. The differences in diagnostic values of PCT, hs-CRP, WBC and NEU% between Gram-negative group and Gram-positive group were analyzed by using receiver operating characteristic (ROC) curve and it was plotted to assess the prognostic values of PCT, hs-CRP, WBC and NEU% for septic patients with blood stream infection. Results Compared with Gram-positive group, the levels of PCT [55.32(22.01, 97.11)vs. 2.13(0.27, 5.27)](P<0.01), hs-CRP[105.09(69.97, 186.12)vs. 70.54(42.37, 138.63)](P=0.508), NEU%[88.30(75.79, 93.52)vs.55.32(22.01, 97.11)](P=0.302)were higher but WBC was lower[13.59(10.74, 17.58)vs.13.73(11.32, 20.90)](P=0.058)in Gram-negative group.The ROC curve analysis of PCT showed the area under the curve (AUC) was 0.867 (95%CI: 0.789-0.946). When the optimal cutoff point of PCT was 17.48 ng/mL, the largest Youden’s index was found to be 0.661 with 76.9% sensitivity and 89.2% specificity. Between two groups, there were significant differences in APACHEⅡ score and SOFA score (27.46±9.60 vs.23.67±7.74, P=0.020; 8.05±3.38 vs.6.59±3.45, P=0.028). There was significant difference in diagnostic value between PCT and SOFA (r=0.536, P=0.036) in Gram-negative group but no significant difference in Gram-positive group. Conclusions Higher PCT levels are found in Gram-negative group and it can play a role in differntiation between the Gram-negative group and Gram-positive group rather than hs-CRP, WBC and NEU%. PCT can be a better indicator for evaluation of severity of sepsis as well as for prognosis of sepsis patients with Gram-negative bacterium infection. Key words: Procalcitonin; Gram-negative bacterium; Gram-positive bacterium; Blood infection