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Reference: Burstein B, et al. Prediction of Bacteremia and Bacterial Meningitis Among Febrile Infants Aged 28 Days or Younger. JAMA. Published online December 08, 2025. Date: April 3, 2026 Dr. Margarita Ramos Guest Skeptic: Dr. Margarita Ramos is a pediatric hospitalist at Children’s National Hospital in Washington, D.C., and Assistant Professor of Pediatrics at the George Washington University School of Medicine and Health Sciences where completed the Master Teacher Leadership Development Program in 2024. Her scholarly interests include equity in medical education and health services research. Case: A 12-day-old boy is brought to the emergency department (ED) by his parents for fever. At home, he felt a little warm, so they took his temperature and found it was 38.3°C. The family called the boy’s pediatrician, who told them to bring him to the ED immediately. The baby has been feeding well. He has had a normal number of wet diapers and stools. He has no other medical history and was born full-term. On your exam, the baby looks good. There is no obvious source for his fever. His parents say to you: “Our pediatrician told us that fevers at this age are worrisome, and our baby may need a lot of testing, including something called a lumbar puncture. We looked it up, and it sounds really scary. Do we have to do all that?” Background: We’re back on the topic of well-appearing febrile infants, and things have changed! Specifically, the “limbo” bar of age for which of the infants requiring a lumbar puncture (LP) has dropped quite a bit. Some may recall practicing at a time when any febrile babies ≤3-months-old were getting an LP. Later, that bar had dropped down to febrile babies ≤28 days getting an LP. Along the way, we’ve had various tools to help guide us in identifying babies at low risk for what was once termed a serious bacterial infection (SBI), including urinary tract infection, bacteremia, and bacterial meningitis. These included tools like the Philadelphia, Rochester, and Boston criteria that risk-stratified based on pre-determined thresholds for temperature, lab tests, urine studies and more. In 2019, the Pediatric Emergency Care Applied Research Network (PECARN) derived and validated a clinical decision rule for identifying low-risk febrile infants based on urine, absolute neutrophil count (ANC) and procalcitonin. We covered this study in SGEM#296. The rounded PECARN Rule is: Negative urinalysis Absolute Neutrophil Count (ANC) ≤4,000/µL Serum procalcitonin ≤0.5 ng/ml In 2021, we saw the limbo bar drop again with new guidance from the American Academy of Pediatrics (AAP) covered on SGEM#341. The age for LP moved down to 22 days. Based on this guideline, the decision to perform LP on infants from 22 to 28 days could be guided by inflammatory markers. There was also another shift. Instead of focusing on SBIs, which included UTIs, one of the most common sources of infection, researchers started to focus on bacteremia and bacterial meningitis, termed invasive bacterial infections (IBIs), which have very bad consequences if missed. Right now, the bar sits around 21–22 days because that’s where the data feels comfortable. And to be fair, newborns are different from older infants. Their immune systems are immature, their symptoms are subtle, and the consequences of missing meningitis are enormous. So naturally, we are cautious. Clinical Question: How accurately can the PECARN rule identify febrile infants 28 days or younger at low risk for invasive bacterial infections? Dr. Brett Burstein Reference: Burstein B, et al. Prediction of Bacteremia and Bacterial Meningitis Among Febrile Infants Aged 28 Days or Younger. JAMA. Published online December 08, 2025. Population: well-appearing febrile infants ≤ 28 days, temperature ≥38°C, from four prospective cohort studies across six countries within the global Pediatric Emergency Research Network (PERN) who underwent testing with PECARN rule components (pro