PECARN and the AAP febrile infant guideline

  • Published March 2, 2023

Caring for babies with fevers is complicated because some of these infants may have life-threatening invasive bacterial infections, such as bacterial meningitis or bacteremia (bacteria in the blood). This group of infections is called serious bacterial illnesses (SBIs). In 2021 the American Academy of Pediatrics (AAP) published a clinical practice guideline for the care of babies with fevers. The guideline uses blood tests and the height of the fever to identify infants who are at risk for SBIs.

EMSC’s research arm, the Pediatric Emergency Care Applied Research Network (PECARN), has conducted large-scale, multicenter studies to determine which well-appearing infants with fevers need blood testing and spinal taps. These studies were integrated into the AAP guidelines and help doctors know which tests to order and when. But not all hospitals have access to all of the blood tests proposed. PECARN’s Nathan Kuppermann, MD, MPH, Prashant Mahajan, MD, MPH, MBA, and Peter Dayan, MD, MSc shared their tips in "Fever, ANC, Procalcitonin and the AAP Febrile Infant Guidelines,” published this January.

PECARN AAP febrile infant guidelines chart

Height of fever

In the past, physicians used the height of fever to help determine the need for a comprehensive laboratory evaluation, usually including a lumbar puncture (LP). The AAP guideline also classifies a temperature of > 38.5 C as a risk factor for SBI. But PECARN studies identified the biomarker procalcitonin (PCT) as the most important marker for SBI. When used in conjunction with the absolute neutrophil count (ANC) and the urinalysis (UA), the height of fever is no longer a significant factor at identifying young febrile infants with SBIs. The height of fever alone should not drive a work-up when the patient has a normal UA, ANC and PCT. But it is important when clinicians do not have PCT available.

Blood work/biomarkers

The ANC is a blood test that is part of the complete blood count (CBC) and often elevated as a marker of infection. PECARN studies identified that the ANC is a better marker for SBIs than the traditionally used white blood cell (WBC). PCT is another blood marker suggestive of bacterial infection that performs better than any other commonly used markers, but not all hospitals have access to this test. The PECARN febrile infant studies show that the ANC and PCT, when used in conjunction with the UA, best identify infants who may have SBIs and those who don’t. For those at low risk, this results in decreased need for invasive blood and spinal fluid testing.


The tests PCT and ANC are valuable blood tests that improve doctors' ability to identify which well-appearing infants with fevers have SBIs and need more testing and treatment.

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