An Evaluation of Serum Procalcitonin and C-Reactive Protein Levels as Diagnostic and Prognostic Biomarkers of Severe Sepsis

Abstract

Background: Recommendations have been made, following the multicenter Surviving Sepsis Campaign study, to standardize the definition of severe sepsis with reference to several parameters such as haemodynamic stability, acid-base balance, bilirubin, creatinine, International Normalized Ratio (INR), urine output and pulmonary functional value of the ratio between arterial oxigen partial pressure and inspiratory oxigen concentration. Procalcitonin (PCT) is considered to be a gold standard biomarker for the inflammatory response, and recent studies have shown that it may help to discover whether a seriously ill person is developing sepsis. C-reactive protein (CRP) is also used as a marker of inflammation in the body, as its blood levels increase if there is any inflammation in the body. The aim of this study was to evaluate serum procalcitonin and C-reactive protein levels as diagnostic and prognostic biomarkers of severe sepsis.

Material and method: Sixty patients, diagnosed as being "septic", were admitted to the intensive care unit (ICU). Based on laboratory results and clinical findings a diagnosis of "severe sepsis" was made, and correlated with PCT and CRP values. The APACHE II, SAPS II and SOFA severity scores were calculated, analyzed and correlated with PCT and CRP.

Results: Fifty two patients (86.67%) presented with criteria for severe sepsis. Multivariate correlation analysis indicated a significant positive association between procalcitonin and all severity scores (APACHEII p<0.0001, SOFA p<0.0001, SAPS II p<0.0001). CRP proved to be significantly correlated only with the SAPS II score (p=0.0145). Mortality rate was high, with 48 patients (80%) dying. There was no significant correlation between the levels of the PCT and CRP biomarkers and severe sepsis (p=0.2059 for PCT, p=0.6059 for CRP).

Conclusions: The procalcitonin levels are highly correlated with the severity scores (APACHE II, SAPS II, SOFA) regularly used in ICUs and therefore can be used for determining the severity of the septic process. Quantitive procalcitonin and C-reactive protein analysis was not shown to be useful in diagnosing severe sepsis. However, PCT and CRP can be used to predict the fatal progression of the septic patient.

Keywords: C-reactive protein; procalcitonin; prognostic biomarkers; severe sepsis.

Figure 1

Survival curve at 6 months for patients with severe sepsis vs sepsis

Figure 2

Comparative ROC curves for PCT, CRP, APACHE II, SAPS II and SOFA for predicting mortality