Role of Procalcitonin and C-reactive protein in differentiating culture negative bacterial sepsis and systemic inflammatory response

Background: It is very important to distinguish between non-infectious systemic inflammatory response (SIRS) and culture negative sepsis as the management of the two conditions is different this often creates diagnostic challenge in day to day practice. The aim of present study is to investigate the diagnostic accuracy of serum PCT and CRP to differentiate between culture negative bacterial sepsis and non-infective SIRS. We have also studied their diagnostic efficacy in culture-positive sepsis. Materials and methods: 178 cases who were admitted in acute medical care unit in tertiary care centre, were included in the study. The cases were divided into three groups. Group I (culture positive sepsis) patients with positive microbial culture and 2 or more signs of sepsis. Group II (culture negative sepsis) includes patients with 2 or more sign of SIRs and clinical suspicion of infection with negative culture result. Group III (non-infective SIRs) includes patient with 2 or more sign of SIRS without evidence of any infection. Samples were collected for blood culture, differential count, PCT and CRP along with other routine investigation. The diagnostic performance of PCT and CRP was demonstrated with ROC curve analysis. Results: The median Procalcitonin was approximately 9 fold higher in culture negative group compared to non-infective SIRS and it was statistically significant (P<0.01) whereas CRP showed only 2-3 fold increase between these groups. ROC curve analysis for PCT and CRP between culture negative and SIRS groups for prediction of systemic infection were performed. The area under the curve for PCT and CRP were 0.986 and 0.785 respectively. Conclusion: Biomarkers such as PCT and CRP are strongly associated with infection likelihood and sepsis and they can serve as useful adjuncts to routine clinical information. These markers were also able to distinguish between patients with non-infective SIRS and sepsis.