Procalcitonin does discriminate between sepsis and systemic inflammatory response syndrome

Aims: To evaluate whether procalcitonin ( PCT) and C reactive protein (CRP) are able to discriminate between sepsis and systemic inflammatory response syndrome ( SIRS) in critically ill children. Methods: Prospective, observational study in a paediatric intensive care unit. Kinetics of PCT and CRP were studied in patients undergoing open heart surgery with cardiopulmonary bypass (CPB) ( SIRS model; group I-1) and patients with confirmed bacterial sepsis ( group II). Results: In group I, PCT median concentration was 0.24 ng/ml ( reference value <2.0 ng/ml). There was an increment of PCT concentrations which peaked immediately after CPB ( median 0.58 ng/ml), then decreased to 0.47 ng/ml at 24 h; 0.33 ng/ml at 48 h, and 0.22 ng/ml at 72 h. CRP median concentrations remained high on POD1 (36.6 mg/l) and POD2 (13.0 mg/l). In group II, PCT concentrations were high at admission ( median 9.15 ng/ml) and subsequently decreased in 11/14 patients who progressed favourably ( median 0.31 ng/ml). CRP levels were high in only 11/14 patients at admission. CRP remained high in 13/14 patients at 24 h; in 12/14 at 48 h; and in 10/14 patients at 72 h. Median values were 95.0, 50.9, 86.0, and 20.3 mg/l, respectively. The area under the ROC curve was 0.99 for PCT and 0.54 for CRP. Cut off concentrations to differentiate SIRS from sepsis were >2 ng/ ml for PCT and >79 mg/l for CRP. Conclusion: PCT is able to differentiate between SIRS and sepsis while CRP is not. Moreover, unlike CRP, PCT concentrations varied with the evolution of sepsis.