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Daily assay of procalcitonin, C-reactive protein and IL-6 roles in diagnosis and management of severe sepsis


Early diagnosis of sepsis is crucial for management and outcome of critically ill patients. The use of clinical parameters, white cell count or body temperature proved far from ideal in identifying patients who need antimicrobial therapy. The lack of a sensible and specific marker of infection may be responsible for delaying or prolonging antibiotic use [1]. The aims of this work were to test the predictive ability of the serial monitoring of IL-6, procalcitonin (PCT), and C-reactive protein (CRP) to stratify the different levels of sepsis and to assess whether their measurement could add to the therapeutic decision-making process during long-term ICU stay.


In a prospective observational study we studied the time course of inflammatory markers in consecutive cases of long-term critical illness in the general ICU of a university hospital. Daily sera were subsequently analyzed for CRP, PCT and IL-6 (only in the last 16 patients) in all patients with length of stay >6 days.


We enrolled 26 patients, for a total of 592 days. In seven patients that never experienced severe sepsis/septic shock CRP, PCT and IL-6 levels decreased over time, the 14 who recovered had a reduction of markers, while no variation was found in five patients expired in sepsis. One hundred and ninety-eight days classified as severe sepsis/septic shock had CRP (72.1 (43.4 to 127.8 IQR) vs. 90.8 (46.8 to 213.9)), PCT (0.19 (0.09 to 0.49) vs. 1.9 (0.49 to 4.92)) and IL-6 (83.90 (57.25 to 133.85) vs. 199.18 (105.51 to 289.27)) higher than 394 SIRS/sepsis days, P < 0.001. Prediction of severe sepsis/septic shock (receiver operating characteristic area) was 0.59 ± 0.03 for CRP, 0.82 ± 0.02 for PCT and 0.76 ± 0.03 for IL-6 (P < 0.001). Forty-four antibiotic courses were recorded; the initial value of markers was higher than the last day, and mean course values were higher than those without antibiotics. Adopting 0.25 ng/ml as the PCT cutoff value between infection expected to be treated with antibiotics and inflammation without the need for antibiotic therapy, inappropriate antibiotic treatment was given on 202/592 days.


Daily measure of PCT, at variance of CRP or IL-6, is accurate in discriminating a day spent in severe sepsis/septic shock. An antimicrobial therapy policy based only on clinical diagnosis proved ineffective, with 34% of inappropriate days that could have been saved using a PCT-guided antibiotic strategy.


  1. Nobre V, et al.: Use of procalcitonin to shorten antibiotic treatment duration in septic patients: a randomized trial. Am J Respir Crit Care Med 2008, 177: 498-505. 10.1164/rccm.200708-1238OC

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Umbrello, M., Marzorati, S., Mantovani, E. et al. Daily assay of procalcitonin, C-reactive protein and IL-6 roles in diagnosis and management of severe sepsis. Crit Care 13 (Suppl 1), P384 (2009).

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  • Severe Sepsis
  • Critical Illness
  • Antimicrobial Therapy
  • Prospective Observational Study
  • Procalcitonin