There are many milestones celebrated during the first year of a child’s life. For some parents, the two-month mark may be the biggest, offering the relief that an infant fever no longer means an automatic lumbar puncture. But wouldn’t it be great if we could really predict sick vs not sick in infants without the lumbar puncture? We might be getting closer.

Authors of the PECARN cohort trial published a secondary analysis that evaluated the prevalence of bacterial meningitis and bacteremia in healthy infants within 60 days old presenting to emergency departments with fever  over 38°C and a positive urinalysis. More than 7,000 infants with a urinalysis, blood culture, and cerebral spinal fluid available for review were included in this secondary analysis. Many also had a procalcitonin and absolute neutrophil count (ANC), all of which are part of PECARN prediction criteria for severe bacterial infections in infants 29-60 days old. About 15 percent of the infants analyzed had a positive urinalysis (57% male, 32% ≤ 28 days old), defined as the presence of nitrates, any leukocyte esterase, or more than five white blood cells per high-power field.

While about half of the infants with a positive urinalysis had culture-positive urinary tract infections, they were extremely unlikely to have bacterial meningitis or bacteremia. And by extremely unlikely, we mean zero percent – there were no cases of meningitis or bacteremia in infants 29-60 days old with a positive urinalysis or in those under 60 days old with positive urinalysis, procalcitonin < 0.5 ng/mL, and ANC < 4 × 103 cells/mm3. Only 0.2 percent of infants with a negative urinalysis were found to have bacterial meningitis and 1.1 percent were bacteremic.

These data highlight the implications of practicing with a bias towards action (as opposed to inaction) when the evidence is lacking. In the past, we had research to say that clinical judgment alone was inadequate for predicting which febrile babies might have meningitis, but we didn’t have any other tools to help us reliably predict sick vs not sick without invasive diagnostic testing. So at the time, the path clearly chosen by experts and professional organizations was towards doing a lumbar puncture even if that meant 100,000 babies got a lumbar puncture to save one unrecognized case of meningitis. But now the prevalence of meningitis is lower and this ratio would be closer to a million babies getting lumbar punctures to find one case of meningitis. Today, thanks to this study and its parent PECARN cohort, the evidence is no longer lacking and we no longer have to enact so much philosophical bias in our decision making. We can use urinalyses and the validated lab-based PECARN criteria to predict which febrile infants have a serious bacterial infection without doing lumbar punctures on all of them. One last exciting outcome here we have to mention: we finally found a situation where procalcitonin is actually useful!


Practice Point: Febrile infants 29-60 days old with a positive urinalysis and those ≤ 28 days old with low-risk PECARN criteria have an extremely low likelihood of bacterial meningitis and can be spared the lumbar puncture.

EBM Pearl: A philosophical bias towards action leads to overdiagnosis and overtreatment whereas a bias towards inaction risks unrecognized and untreated disease. Pick your poison (or rather, practice philosophy) until the data are in.

Reference: Pediatrics. 2022 Oct 1;150(4):e2021055633

For more information, see the topic Fever Without Apparent Source in Infants and Young Children in DynaMed.