Objectives To determine whether peak blood PCT measured within 48 hours of pediatric intensive care unit (PICU) admission can differentiate severe bacterial infections from sterile inflammation and viral infection and identify potential subgroups of PICU patients for whom PCT may not have clinical utility. Study design This was a retrospective, observational study of 646 critically ill children who had PCT measured within 48 hours of admission to an urban, academic PICU. Patients were stratified into 6 categories by infection status. We compared test characteristics for peak PCT, C-reactive protein (CRP), white blood cell count (WBC), absolute neutrophil count (ANC), and percentage immature neutrophils (% Imm). The area under the receiver operating characteristic curve (AUROC) was determined for each biomarker to discriminate bacterial infection. Results The AUROC was similar for PCT (0.73, 95% CI 0.69, 0.77) and CRP (0.75, 95% CI 0.71, 0.79; p=0.36), but both outperformed WBC, ANC, and % immature neutrophils (p<0.01 for all pairwise comparisons). The combination of PCT and CRP was no better than either PCT or CRP alone. Diagnostic patterns prone to false-positive and false-negative PCT values were identified. Conclusions Peak blood PCT measured close to PICU admission was not superior to CRP in differentiating severe bacterial infection from viral illness and sterile inflammation; both PCT and CRP outperformed WBC, ANC, and % immature neutrophils. PCT appeared especially prone to inaccuracies in detecting localized bacterial central nervous system infections or bacterial co-infection in acute viral illness causing respiratory failure.

We retrospectively studied the effect of introducing procalcitonin into clinical practice on antibiotic use within a large academic pediatric intensive care unit. In the absence of a standardized algorithm, availability of the procalcitonin assay did not reduce the frequency of antibiotic initiations or the continuation of antibiotics for greater than 72 hours.