Febrile Infants ≤60 Days Old With Positive Urinalysis Results and Invasive Bacterial Infections.

Objectives: We aimed to describe the clinical and laboratory characteristics of febrile infants ≤60 days old with positive urinalysis results and invasive bacterial infections (IBI).

Methods: We performed a planned secondary analysis of a retrospective cohort study of febrile infants ≤60 days old with IBI who presented to 11 emergency departments from July 1, 2011, to June 30, 2016. For this subanalysis, we included infants with IBI and positive urinalysis results. We analyzed the sensitivity of high-risk past medical history (PMH) (prematurity, chronic medical condition, or recent antimicrobial receipt), ill appearance, and/or abnormal white blood cell (WBC) count (<5000 or >15 000 cells/μL) for identification of IBI.

Results: Of 148 febrile infants with positive urinalysis results and IBI, 134 (90.5%) had bacteremia without meningitis and 14 (9.5%) had bacterial meningitis (11 with concomitant bacteremia). Thirty-five infants (23.6%) with positive urinalysis results and IBI did not have urinary tract infections. The presence of high-risk PMH, ill appearance, and/or abnormal WBC count had a sensitivity of 53.4% (95% confidence interval: 45.0-61.6) for identification of IBI. Of the 14 infants with positive urinalysis results and concomitant bacterial meningitis, 7 were 29 to 60 days old. Six of these 7 infants were ill-appearing or had an abnormal WBC count. The other infant had bacteremia with cerebrospinal fluid pleocytosis after antimicrobial pretreatment and was treated for meningitis.

Conclusions: The sensitivity of high-risk PMH, ill appearance, and/or abnormal WBC count is suboptimal for identifying febrile infants with positive urinalysis results at low risk for IBI. Most infants with positive urinalysis results and bacterial meningitis are ≤28 days old, ill-appearing, or have an abnormal WBC count.