Is 15 days an appropriate cut-off age for considering serious bacterial infection in the management of febrile infants?

INTRODUCTION: Febrile infants <3 months of age have a greater risk for serious bacterial infection (SBI). The risk is inversely correlated with age. Most protocols recommend admitting to hospital all febrile infants <28 days of age. However, as the prevalence of SBI is not homogenous in this age group, some authors have considered decreasing this cut-off age, allowing ambulatory management of selected patients meeting low-risk criteria.

OBJECTIVE: To determine whether 15 days is a suitable cut-off age for different approaches to the management of infants with fever.

PATIENTS AND METHODS: Cross-sectional descriptive study of infants <3 months of age with fever without a source seen between September 1, 2003 and August 30, 2010 in the pediatric emergency department of a tertiary teaching hospital. All infants <3 months of age with fever without a source (≤ 38 °C) were included. The following data were collected: age, sex, temperature, diagnosis, management in pediatric emergency department, and outcome.

RESULTS: Data were collected for 1575 infants; of whom, 311 (19.7%, 95% confidence intervals [CI]: 17.7-21.7) were found to have an SBI. The rate of SBI in the patients who were 15 to 21 days of age was 33.3% (95% CI: 23.7%-42.9%), similar to that among infants who were 7 to 14 days of age (31.9%, 95% CI: 21.1%-42.7%) and higher than among those older than 21 days of age (18.3%, 95% CI: 16.3-20.3%).

CONCLUSIONS: Febrile infants 15 to 21 days of age had a rate of SBI similar to younger infants and higher than older age infants. It is not appropriate to establish the approach to management of infants with fever based on a cut-off age of 2 weeks.