• Karen Milcent, Sabine Faesch, Christèle Gras-Le Guen, François Dubos, Claire Poulalhon, Isabelle Badier, Elisabeth Marc, Christine Laguille, Loïc de Pontual, Alexis Mosca, Gisèle Nissack, Sandra Biscardi, Hélène Le Hors, Ferielle Louillet, Andreea Madalina Dumitrescu, Philippe Babe, Christelle Vauloup-Fellous, Jean Bouyer, and Vincent Gajdos.
• Department of Pediatrics, Antoine Béclère University Hospital, Assistance Publique-Hôpitaux de Paris, Clamart, France2INSERM, CESP Centre for Research in Epidemiology and Population Health, Paris-Sud, Paris-Saclay University, Villejuif, France.
• JAMA Pediatr. 2016 Jan 1; 170 (1): 62-9.

ImportanceThe procalcitonin (PCT) assay is an accurate screening test for identifying invasive bacterial infection (IBI); however, data on the PCT assay in very young infants are insufficient.ObjectiveTo assess the diagnostic characteristics of the PCT assay for detecting serious bacterial infection (SBI) and IBI in febrile infants aged 7 to 91 days.Design, Setting, And ParticipantsA prospective cohort study that included infants aged 7 to 91 days admitted for fever to 15 French pediatric emergency departments was conducted for a period of 30 months (October 1, 2008, through March 31, 2011). The data management and analysis were performed from October 1, 2011, through October 31, 2014.Main Outcomes And MeasuresThe diagnostic characteristics of the PCT assay, C-reactive protein (CRP) concentration, white blood cell (WBC) count, and absolute neutrophil cell (ANC) count for detecting SBI and IBI were described and compared for the overall population and subgroups of infants according to the age and the duration of fever. Laboratory test cutoff values were calculated based on receiver operating characteristic (ROC) curve analysis. The SBIs were defined as a pathogenic bacteria in positive culture of blood, cerebrospinal fluid, urine, or stool samples, including bacteremia and bacterial meningitis classified as IBIs.ResultsAmong the 2047 infants included, 139 (6.8%) were diagnosed as having an SBI and 21 (1.0%) as having an IBI (11.0% and 1.7% of those with blood culture (n = 1258), respectively). The PCT assay offered an area under the curve (AUC) of ROC curve similar to that for CRP concentration for the detection of SBI (AUC, 0.81; 95% CI, 0.75-0.86; vs AUC, 0.80; 95% CI, 0.75-0.85; P = .70). The AUC ROC curve for the detection of IBI for the PCT assay was significantly higher than that for the CRP concentration (AUC, 0.91; 95% CI, 0.83-0.99; vs AUC, 0.77; 95% CI, 0.65-0.89; P = .002). Using a cutoff value of 0.3 ng/mL for PCT and 20 mg/L for CRP, negative likelihood ratios were 0.3 (95% CI, 0.2-0.5) for identifying SBI and 0.1 (95% CI, 0.03-0.4) and 0.3 (95% CI, 0.2-0.7) for identifying IBI, respectively. Similar results were obtained for the subgroup of infants younger than 1 month and for those with fever lasting less than 6 hours.Conclusions And RelevanceThe PCT assay has better diagnostic accuracy than CRP measurement for detecting IBI; the 2 tests perform similarly for identifying SBI in febrile infants aged 7 to 91 days.

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