Objective Analyse procalcitonin value in clinical practice for diagnosis of sepsis, classification of sepsis severity and prognosis evaluation, in critically ill children.

Results We designed several studies to find procalcitonin and C-reactive protein (CRP) cut-off values for diagnosis of sepsis. The cut-off value for procalcitonin was 1.1 ng/ml and for CRP was 5.6 ng/ml with an area under the receiver operator characteristic curve of 0.91 (95% CI 0.88 to 0.94) and 0.75 (95% CI 0.69 to 0.80), respectively. Procalcitonin values increase as sepsis severity increases. Procalcitonin values higher than 5.0 ng/ml and 20.0 ng/ml were very common in severe sepsis and septic shock, respectively. Procalcitonin values between 0.25 and 0.50 ng/ml were usually present in localised infection. Procalcitonin could be used for the early identification of critically ill children who are at high risk of mortality. In our experience, procalcitonin values higher than 100 ng/ml could serve as a marker of mortality, especially if the values do not decrease after 24 h.

Conclusions Absolute values of procalcitonin are useful but the dynamics of procalcitonin levels could be more important. Procalcitonin should be determined when a clinical suspicion of sepsis or shock is present. In our patients, procalcitonin values lower than 1 ng/ml indicate the absence of sepsis, but localised infection could be present. Persistently high or increasing procalcitonin values mean that the process we are managing is out of control and we have to change our therapeutic approach, whereas decreasing procalcitonin values mean good evolution without the need to change therapy.