Procalcitonin and C-reactive protein as markers of systemic inflammatory response syndrome severity in critically ill children

Objectives: To analyse the clinical value of procalcitonin (PCT), C-reactive protein (CRP) and leucocyte count in the diagnosis of paediatric sepsis and in the stratification of patients according to severity. Design: Prospective, observational study. Setting: Paediatric intensive care unit (PICU). Patients: Ninety-four children. Measurement and results: Leucocyte count, PCT and CRP were measured when considered necessary during the PICU stay. Patients were classified, when PCT and CRP were measured, into one of six categories (negative, SIRS, localized infection, sepsis, severe sepsis, and septic shock) according to the definitions of the American College of Chest Physicians/Society of Critical Care Medicine. A total of 359 patient day episodes were obtained. Leucocyte count did not differ across the six diagnostic classes considered. Median plasma PCT concentrations were 0.17, 0.43, 0.79, 1.80, 15.40 and 19.13 ng/ml in negative, systemic inflammatory response syndrome (SIRS), localized infection, sepsis, severe sepsis, and septic shock groups, respectively, whereas median plasma CRP concentrations were 1.35, 3.80, 6.45, 5.70, 7.60 and 16.2 mg/dl, respectively. The area under the ROC curve for the diagnosis of septic patients was 0.532 for leucocyte count (95% CI, 0.462-0.602), 0.750 for CRP (95% CI, 0.699-0.802) and 0.912 for PCT (95% CI, 0.882-0.943). We obtained four groups using CRP values and five groups using PCT values that classified a significant percentage of patients according to the severity of the different SIRS groups. Conclusions: PCT is a better diagnostic marker of sepsis in critically ill children than CRP. The CRP, and especially PCT, may become a helpful clinical tool to stratify patients with SIRS according to disease severity.