To study the behavior of procalcitonin and to verify whether it can be used to differentiate children with septic conditions.

Children were enrolled prospectively from among those aged 28 days to 14 years, admitted between January 2004 and December 2005 to the pediatric intensive care unit at UNESP with sepsis or septic shock. The children were classified as belonging to one of two groups: the sepsis group (SG; n = 47) and the septic shock group (SSG; n = 43). Procalcitonin was measured at admission (T0) and again 12 hours later (T12h), and the results classed as: < 0.5 ng/mL = sepsis unlikely; ≥ 0.5 to < 2 = sepsis possible; ≥ 2 to < 10 = systemic inflammation and ≥ 10 = septic shock.

At T0 there was a greater proportion of SSG patients than SG patients in the highest PCT class [SSG: 30 (69.7%) > SG: 14 (29.8%); p < 0.05]. The proportion of SSG patients in this highest PCT class was greater than in all other classes (≥ 10 = 69.7%; ≥ 2 to < 10 = 18.6%; ≥ 0.5 to < 2 = 11.6%; < 0.5 = 0.0%; p < 0.05). The behavior of procalcitonin at T12h was similar to at T0. The pediatric risk of mortality (PRISM) scores for the SSG patients in the highest procalcitonin class were more elevated than for children in the SG [SSG: 35.15 (40.5-28.7) vs. SG: 18.6 (21.4-10.2); p < 0.05].

Procalcitonin allows sepsis to be differentiated from septic shock, can be of aid when diagnosing septic conditions in children and may be related to severity.