Prevalence and Management of Invasive Bacterial Infections in Febrile Infants Ages 2 to 6 Months.

STUDY OBJECTIVE: Validated prediction rules identify febrile neonates at low risk for invasive bacterial infection. The optimal approach for older febrile infants, however, remains uncertain. METHODS: We performed a retrospective cohort and nested case-control study of infants 2 to 6 months of age presenting with fever (≥38.0 °C) to 1 of 5 emergency departments. The study period was from 2011 to 2019. The primary outcome was invasive bacterial infection, defined by the growth of pathogenic bacteria from either blood or cerebrospinal fluid culture. Secondary outcomes included obtaining bacterial cultures (blood, cerebrospinal fluid, or urine), administering antibiotics, and hospitalization. For the nested case-control study, we age-matched infants with invasive bacterial infection to 3 infants without invasive bacterial infection, sampled from the overall cohort. RESULTS: There were 21,150 eligible patient encounters over 9-years, and 101 infants had a documented invasive bacterial infection (0.48%; 95% confidence interval [CI], 0.39% to 0.58%). Invasive bacterial infection prevalence ranged from 0.2% to 0.6% among the 5 sites. The frequency of bacterial cultures ranged from 14.5% to 53.5% for blood, 1.6% to 12.9% for cerebrospinal fluid, and 31.8% to 63.2% for urine. Antibiotic administration varied from 19.2% to 46.7% and hospitalization from 16.6% to 28.3%. From the case-control study, the estimated invasive bacterial infection prevalence for previously healthy, not pretreated, and well-appearing febrile infants was 0.32% (95% CI, 0.24% to 0.41%). CONCLUSION: Although invasive bacterial infections were uncommon among febrile infants 2 to 6 months in the emergency department, the approach to diagnosis and management varied widely between sites. Therefore, evidence-based guidelines are needed to reduce low-value testing and treatment while avoiding missing infants with invasive bacterial infections.