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    PECARN Rule for Low Risk Febrile Infants 29-60 Days Old

    Predicts risk of urinary tract infection, bacteremia, or bacterial meningitis in febrile infants age 29-60 days old.


    This calculator is not yet externally validated. While derived in infants aged 0-60 days, the creators recommend using this calculator only in infants aged 29-60 days (i.e., do not use in infants 28 days or younger), due to elevated herpes meningoencephalitis risk and and limited numbers of episodes of bacterial meningitis in that age group (see Pearls/Pitfalls and Creator Insights for details).


    Does not apply to ill-appearing infants. The rule is intended to be one-directional: it may help rule out serious bacterial infection (SBI) in patients who are “low risk”, but the converse is not true (i.e., patients who are “not low risk” by the rule do not necessarily have SBI).

    When to Use
    Why Use

    Well-appearing infants 29-60 days old, to stratify risk of SBI (defined as urinary tract infection, bacteremia, or bacterial meningitis).

    • The majority of infants younger than 60 days old are unvaccinated and have immature immune systems.

    • Infants with signs of shock or who are otherwise ill-appearing/unstable should be considered at high risk of SBI and in most cases should have blood, urine, and CSF cultures collected. This clinical prediction rule would not apply to such patients.

    • Serum procalcitonin level is required, but may not be rapidly available in all settings.

    • Most SBIs identified in the study were UTIs, so the rule may be less accurate for bacteremia and bacterial meningitis, which have much lower prevalence.

    • Infants 28 days old and younger warrant special attention, as they are at elevated risk of herpes meningoencephalitis as well as a more rapid progression of disease. The study authors recommend a full laboratory evaluation, including CSF, for those 28 days and younger.

    • In the study, three infants were misclassified as being low risk but did have SBIs (two UTI, and one Enterobacter cloacae bacteremia). All were treated appropriately based on culture results and had uneventful clinical courses.

    • As noted in the Supplement, alternative cutoffs for ANC (4,000) and procalcitonin (0.5) were studied and found to be comparable to the published cutoffs in terms of accuracy. Per the authors of the study, clinicians should consider using these cutoffs as they are easier, safer, and less confusing to use clinically, and had minimal impact on accuracy of the rule (see Creator Insights for details).

    • Physical exam alone is unreliable in ruling out SBI in febrile infants.

    • May avoid unnecessary lumbar punctures, empirical antibiotics, and hospital admissions. 

    • Helps determine disposition of some well-appearing infants who can reliably follow up with their primary pediatrician or in the ED in 24 hours and/or can be relied upon to return to the ED should a pending culture return positive.



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    Next Steps
    Creator Insights


    Some well-appearing infants 29-60 days old with low risk for SBI may be suitable for discharge from the ED with follow up with their primary pediatrician or in the same ED in 24 hours for reassessment. Infants younger than 29 days old generally require admission for close monitoring and empiric IV antibiotics.


    • Patients deemed low risk by this rule might be safely discharged from the ED, as long as follow up with the primary pediatrician or same ED can be reasonably well assured.

    • The decision to admit a febrile infant is multifactorial. Lack of reliable follow up may necessitate admission.

    • For well-appearing immunocompetent infants and children aged 2 months to 2 years presenting with fever and no obvious infectious source, ACEP recommends the following: 

      • Consider chest x-ray if cough, hypoxia, rales, high fever (≥39°C), fever duration greater than 48 hours, or tachycardia/tachypnea out of proportion to fever (level B recommendation).

      • Should not order chest x-ray if wheezing and high likelihood of bronchiolitis (level C recommendation).

      • If dipstick urinalysis is negative and UTI is still suspected, obtain urine culture (level C recommendation).

    Critical Actions

    Remember to consider a critical congenital heart defect (and empiric prostaglandin treatment) in the neonate presenting in shock.

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    Dr. Nathan Kuppermann
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