Markers for Invasive Bacterial Infection in Well-Appearing Young Febrile Infants. The Value of Procalcitonin

BACKGROUND: Serious bacterial infection (SBI) rate is higher among febrile infants under three months of age than among older children. These patients are managed more aggressively and usually several laboratory tests are systematically performed trying to identify those patients in a higher risk of developing a SBI. Recent studies have shown that White Blood Cell (WBC) count has a poor value in the diagnosis of bacteremia and other bacterial infections in this group of age. C-reactive protein (CRP) seems to be a more useful parameter in identify febrile young infants with bacterial infections In the last decade, the procalcitonin (PCT) has been introduced in many protocols for the management of the febrile child in Europe. However, its value among young well-appearing infants is not completely defined. OBJECTIVE: To assess the value of PCT in diagnosing serious bacterial infections and specifically invasive bacterial infections (IBIs) in well-appearing infants under 3 months of age with fever without source (FWS). DESIGN/METHODS: Well-appearing infants under 3 months of age with FWS attended in seven European Paediatric Emergency Departments from the date on which the PCT was introduced at each center were retrospectively included. An IBI was defined when a bacterial pathogen was isolated in blood or cerebrospinal fluid culture. RESULTS: A total of 1,531 infants under 3 months of age with FWS were attended. There were 1,112 well-appearing infants in whom PCT and a blood culture were performed. Among them, 23 (2.1%) were diagnosed with an IBI. A multivariate analysis showed that, among different epidemiological data and blood tests, PCT was the only independent risk factor for having an IBI (OR 21.69 if PCT 650.5 ng/mL). Comparing with C-Reactive Protein, PCT showed a better performance to rule-in an IBI. Among patients with normal urine dipstick and short-evolution fever (less than 6 hours), areas under the ROC curve were 0.819 and 0.563, respectively for detecting IBIs. CONCLUSIONS: Among young infants with FWS, PCT showed a better performance than C-Reactive Protein in identifying patients with IBIs and, mainly in those patients with normal urine dipstick and short-evolution fever, PCT seems to be also the best marker to rule out the presence of an IB