Usefulness of Low-Risk Criteria for Serious Bacterial Infections in Febrile Infants Younger than 90 Days of Age

Abstract

Purpose: To examine the usefulness of simple and quick criteria for identifying febrile infants younger than 90 days with a low risk for serious bacterial infection (SBI). Methods: We conducted a retrospective study of febrile infants younger than 90 days who visited an emergency department (ED) between July 2010 and June 2011. We reviewed their medical history, physical examination findings, levels of white blood cells (WBC) and C-reactive protein (CRP), blood culture, urinalysis, and an analysis of their cerebrospinal fluid (CSF). Patients who met all the following criteria were considered to have a low risk for SBI: (1) an unremarkable medical history, (2) a good appearance, (3) no focal physical signs of infection, (4) WBC 5,000~15,000 /mm3, (5) CRP <2.0 mg/dL, (6) a normal urinalysis, and (7) CSF WBC <25 /mm3 for neonate or <10 /mm3 for infants between 29 days and 90 days. SBI was defined as a positive culture of bacteria from blood, cerebrospinal fluid, or urine. Results: Complete data were available for 493 infants. SBI was documented in 62(12.6%) infants, with 54(11.0%) having a urinary tract infection, 3(0.6%) with bacteremia, 1 (0.2%) with bacterial meningitis, and 4(0.8%) with co-infections. The sensitivity and negative predictive value for SBI from the combination of low-risk criteria was 98.4% and 99.6%, respectively. Conclusion: Although low-risk infants must be carefully observed, our criteria for low-risk might be a reliable and useful tool for excluding SBI for febrile young infants in ED.