<p><strong>OBJECTIVES: </strong>To determine the incidence of bacterial meningitis (BM) among all febrile infants 29-56 days old undergoing a lumbar puncture (LP) in the emergency department of a tertiary care children's hospital and the number of low-risk febrile infants with BM to reassess the need for routine LP in these infants.</p>

<p><strong>STUDY DESIGN: </strong>Retrospective cohort study using a quality improvement registry from July 2007-April 2014. Infants included were 29-56 days old with fever and who had an LP in the emergency department. Low-risk criteria were adapted from the Philadelphia criteria. BM was defined as having a bacterial pathogen isolated from the cerebrospinal fluid. A medical record review of one-third of randomly selected patients in the cohort determined the proportion who met low-risk criteria.</p>

<p><strong>RESULTS: </strong>One of 1188 febrile infants (0.08%) had BM; this patient did not meet low-risk criteria. An additional 40 (3.4%) had positive cerebrospinal fluid cultures; all were contaminants. Subanalysis of one-third of the study population revealed that 45.6% met low-risk criteria; the most common reasons for failing low-risk classification included abnormal white blood cell count or urinalysis.</p>

<p><strong>CONCLUSIONS: </strong>In a cohort of febrile infants, BM is uncommon and no cases of BM would have been missed had LPs not been performed in those meeting low-risk criteria.</p>