Objective: To determine the prevalence of invasive bacterial infection (IBI) in a UK cohort of febrile infants aged 90 days and younger with positive urinalysis (PU) results.
Design: A planned secondary analysis of data from the Febrile Infant Diagnostic Assessment and Outcome study, a prospective multicentre observational cohort study.
Setting: 35 paediatric emergency departments and assessment units across the UK and Ireland, between 6 July 2022 and 31 August 2023.
Patients: Febrile infants aged 90 days and younger presenting to emergency care.
Main outcome measures: IBI rates, namely bacterial meningitis or bacteraemia, among febrile infants with PU results were compared with those with negative urinalysis (NU) results.
Results: 1480 of 1821 infants underwent urinalysis testing. 549 infants had PU results and 931 had NU results. 42/549 (7.7%) and 20/931 (2.2%) infants had IBI in the PU and NU groups, respectively. Of the IBI cases within the PU group, 5/549 (0.9%) were bacterial meningitis and 39/549 (7.1%) were bacteraemia, with two concomitant cases. Of the IBI cases in the NU group, there were 4/931 (0.4%) cases of bacterial meningitis and 18/931 (1.9%) cases of bacteraemia, with two concomitant cases. There were no bacterial meningitis cases in infants over 60 days of age or those with confirmed urinary tract infection (UTI).
Conclusions: The prevalence of bacteraemia was high (7.1%) among PU infants, while the prevalence of bacterial meningitis was low (0.9%), with PU or NU. These findings support existing data that older infants with suspected UTI are at low risk of bacterial meningitis.
Keywords: Infectious Disease Medicine; Paediatric Emergency Medicine.
© Author(s) (or their employer(s)) 2026. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.