Comparison of procalcitonin with C-reactive protein and serum amyloid for the early diagnosis of bacterial sepsis in critically ill neonates and children

Objectives: To evaluate procalcitonin (PCT) as a diagnostic marker of bacterial sepsis in critically ill neonates and children and to compare the results of PCT with those of C-reactive protein (CRP) and serum amyloid (SAA). Design and setting: Prospective, observational study in neonatal and pediatric intensive care units. Patients: A total of 116 divided into four groups according to age and diagnosis: neonates (aged 3-30 days) with sepsis (n = 20), neonates without sepsis (n = 26), children (aged 2-12 years) with sepsis (n = 32), and children without sepsis (n = 38). Interventions: Serum PCT, CRP, and SAA were measured on admission or when a bacterial sepsis was suspected. Area under the receiver operating characteristic (ROC) curve, optimum predictive values, and optimum diagnostic cut off values were evaluated. Results: Admission PCT was significantly higher in neonates and children with sepsis than in the other groups. In the neonates the area under the ROC curve was 0.99 for PCT, 0.95 for CRP, and 0.98 for SAA; in the children it was 1 for PCT, 0.93 for CRP, and 0.96 for SAA. Cutoff concentrations for optimum prediction of sepsis in the neonates were PCT > 6.1 ng/ml (diagnostic efficiency: 93.8%), CRP > 23.0 mg/l (89.7%), and SAA > 41.3 mg/l (95.3%); in the children they were PCT > 8.1 ng/ml (100%), CRP > 22.1 mg/l (89.8%), and SAA > 67.2 mg/l (94.4%). Conclusion: In critically ill children PCT concentration is a better diagnostic marker of sepsis than CRP and SAA. In critically ill neonates, however, PCT, CRP, and SAA are similar diagnostic markers of sepsis. A PCT concentration higher than 8.1 ng/ml identified all children with bacterial sepsis.