Written by Kimi Dunbar
Spoon Feed
Infants less than 90 days with positive viral testing results for flu, COVID, and RSV have lower rates of invasive bacterial infection (meningitis, bacteremia). Infants older than 29 days with positive respiratory testing have even lower rates of invasive bacterial infection.
Synopsis
This planned secondary analysis of the FIDO prospective cohort study evaluated the association between respiratory viral testing and the risk of invasive bacterial infection (IBI) in febrile infants ≤90 days. Conducted across 35 emergency departments in the UK and Ireland, 1,395 infants underwent respiratory viral testing. IBI occurred in 3.8% of infants with negative viral tests and 1.5% with positive tests (p=0.034). Infants ≥29 days with positive viral results had significantly lower IBI rates (0.7%) versus those with negative results (3.2%, p=0.015). Limitations include small IBI cases and site variability. Respiratory viral testing may stratify risk, reducing unnecessary invasive procedures in low-risk infants. (AI-generated)
Test or not?
The AAP guidelines for management of the febrile infant 8-60 days old specifically call for increased research on the role of viral testing. The paper’s findings are not surprising and are consistent with a prior study in 2021. The question is: How much risk of invasive bacterial infection can we tolerate? Personally, I’m not comfortable deferring all blood tests in febrile infants over 29 days with a positive viral test, at least not yet. The AAP currently recommends blood culture and inflammatory markers in well-appearing infants in this age group, and I agree. This study did not consider urinary tract infection as an invasive bacterial infection so did not comment on the relationship between a positive viral test and UTI. While I agree that a missed UTI is of less consequence than meningitis, UTI is a common cause of fever in this population.
Editor’s note: From an EM perspective, I check urinalysis, urine culture, inflammatory markers and blood culture in febrile infants 29-60 days. Also, viral infections lower the accuracy of procalcitonin, so consider this when risk stratifying. ~Clay Smith
Source
Respiratory viral testing for young febrile infants presenting to emergency care: a planned secondary analysis of the Febrile Infants Diagnostic assessment and Outcome (FIDO) prospective observational cohort study. Arch Dis Child. 2024 Nov 19;109(12):988-993. doi: 10.1136/archdischild-2024-327567. PMID: 39357988
