Following study enrolment, baseline (upon ICU admission)anthropometric data (age, sex, height, weight), procalcitonin (PCT) and C-reactive protein (CRP) plasma concentrations and detailed
organ system-oriented medical history were recorded. A venous blood sample was drawn and processed as described in ‘‘Blood collection’’. All patients were followed daily for the presence and
source of infection; other parameters recorded included vital signs,arterial blood gases, complete blood cell count and differential,serum chemistries, administered medications, mechanical ventilation features, and renal replacement. Patients were followed until discharge from the hospital or death. Patients were assigned to groups based on the presence (sepsis-positive, N = 45) or absence
(sepsis-negative, N = 44) of sepsis at any point during their ICU stay.The patients who met the criteria for sepsis during the first24 hours postICU admission were rejected from the study,to rule out subjecs that might have had subclinical sepsis upon ICU entry.