Serum Concentrations of Interleukin-6, Procalcitonin, and C-Reactive Protein: Discrimination of Septical Complications and Systemic Inflammatory Response Syndrome after Pediatric Surgery

BACKGROUND: Early differentiation between sepsis and systemic inflammatory response syndrome (SIRS) is useful for therapeutic management in neonates and infants after surgery. OBJECTIVE: To compare the early (first 2 days) diagnostic value of interleukin-6 (IL-6), procalcitonin (PCT), and C-reactive protein (CRP) after surgery in the differentiation of subsequent SIRS and septic complications. METHODS: IL-6, PCT, and CRP were measured 0, 24, and 48 hours after surgery in neonates and infants with clinical suspicion of postoperative sepsis. Sensitivity, specificity, and predictive values for SIRS/septic complications were calculated. RESULTS: A total of 31 out of 205 neonates and infants showed clinical signs for postoperative sepsis and underwent sepsis work-up. Nine patients developed septic complications, sixteen patients met criteria for SIRS, and six patients showed an uneventful postoperative course during the first five postoperative days. IL-6, PCT, and CRP levels increased in all subgroups after surgery and were significantly higher in the sepsis group (p < 0.05). IL-6 peaked immediately, CRP at 24 to 48 hours, and PCT at 24 hours after surgery. Sensitivity and specificity (area under the curve) for IL-6 (cutoff 673 ng/dL) were 94.4 and 75% (86.2%), for CRP (cutoff 1.48 mg/dL) 76.2 and 75.0% (88.1%), and for PCT (cutoff 16.1 mg/L) 66.7 and 57.1% (65.6%). CONCLUSION: IL-6 appears to be an early marker for severe bacterial infections with high sensitivity. IL-6 and CRP were the most reliable markers for the discrimination between SIRS and sepsis within the postoperative period.