Procalcitonin: a marker to clearly differentiate systemic inflammatory response syndrome and sepsis in the critically ill patient?

Objectives: To define the role of procalcitonin in the differential diagnosis, prognosis and follow-up of critically ill patients. Design: Prospective study during the 2-year period from January 1998-2000. Patients: One hundred nineteen critically ill patients: 29 with systemic inflammatory response syndrome (SIRS) without any signs of infection, I I with sepsis, 17 with severe sepsis, 10 with septic shock and 52 controls. Daily measurements of procalcitonin were performed by an immunocheminoluminometric assay, and values were correlated to the clinical characteristics of the patients. Results: Mean concentrations of procalcitonin were 5.45 (95% CI: 2.11, 8.81), 7.29 (95% CI: -1.92,14.59), 6.26 (95% CI: -1.32, 13.85) and 38.76 ng/ml (95% CI: 0.15, 77.38) on the 1st day in patients with SIRS, sepsis, severe sepsis and septic shock, respectively, and were statistically superior to those of control patients. Procalcitonin was gradually diminished over time with the resolution of the syndrome, while it was sustained in the same or more augmented levels upon worsening. Mean concentrations of procalcitonin on the 1st day for patients finally progressing to ARDS, to ARDS and acute renal failure, to ARDS, acute renal failure and DIC and to ARDS, acute renal failure, DIC and hepatic failure were 10.48, 8.08, 32.72 and 43.35 ng/ml, respectively. ROC curves of the sensitivity and specificity of procalcitonin for the evaluation of SIRS and sepsis were similar. Conclusions: The definite differential diagnosis between SIRS and sepsis may not rely on a single application of procalcitonin but on the complete clinical and laboratory evaluation of the patient with procalcitonin playing a considerable role. Procalcitonin is an early prognostic marker of the advent of MODS; therefore, daily determinations might help in the follow-up of the critically ill patient.