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    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
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    Patent Pending

    Step-by-Step Approach to Febrile Infants

    Identifies febrile infants ≤90 days old at low risk of invasive bacterial infections.


    Use in previously healthy infants ≤90 days old presenting with fever without a source.

    When to Use
    Why Use
    • Previously healthy infants ≤90 days old with documented fever (≥38.0° C or ≥100.4°F) at home or in the emergency department.
    • Use caution in infants with a short duration of fever, as it takes time for serum inflammatory markers like procalcitonin to rise. Consider observation in the ED, even if laboratory values are initially normal.
    • Use caution in infants 21-28 days old, as the management of this age group remains controversial, and the Step-by-Step algorithm did not perform optimally in this group. Among patients with IBI who the Step-by-Step approach failed to identify as high-risk, 4/7 (57%) of these infants were between 21-28 days old. Studies suggest that the prevalence of bacteremia may be higher in infants between 21 and 28 days old, compared to infants >28 days old, and therefore recommend a full sepsis workup for any infant <28 days old (Powell 2018).
    • The Step-by-Step approach was developed with the goal of identifying febrile infants ≤90 days old who are at low risk of invasive bacterial infection, defined as bacteremia or meningitis.
    • This score was only studied in previously healthy infants, and does not apply to infants with any prior medical history.
    • In the study, “fever without a source” was defined as an infant with a normal physical exam without signs or symptoms of a self-limiting viral illness such as bronchiolitis or gastroenteritis.
    • Performs best when applied to infants with fever duration >2 hours because it relies on the detection of inflammatory markers (procalcitonin and C-reactive protein) that may take time to rise.
    • Differences in prevalence of IBI versus non-IBI should also be taken into consideration when interpreting and applying the results of this study.
    • One comparison study showed that Step-by-Step outperformed the Rochester Criteria and Lab-score (Step-by-Step was 92.0% sensitive for ruling out IBI, versus 81.6% for the Rochester Criteria and 59.8% for the Lab-score).

    Etiology of fever in infants ≤90 days old may range from self-limiting viral illness like bronchiolitis to life-threatening invasive bacterial infection (IBI) like bacteremia or meningitis. The Step-by-Step Approach can be used to rule out IBI with high negative predictive value (99.3%). If IBI can be safely ruled out, these low-risk infants do not require hospital admission and intravenous antibiotics.



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    Creator Insights


    Management of invasive bacterial infections in infants:

    • Prompt initiation of broad spectrum antibiotics according to local guidelines is strongly recommended.
    • Optimize respiratory support and hemodynamics if respiratory distress or signs of dehydration or shock are present.
    • Inpatient hospital admission for a minimum of 36-48 hours is recommended if cultures remain negative.

    Studies indicate that 96% of blood cultures will become positive by 36 hours and 99% will become positive by 48 hours, if invasive bacterial infection is present (Biondi 2014, Biondi 2015).

    Critical Actions

    No decision rule should trump clinical gestalt. High suspicion for IBI in a febrile infant should warrant full sepsis workup.

    Content Contributors
    • Emily Heikamp, MD, PhD
    About the Creator
    Dr. Santiago Mintegi
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    Content Contributors
    • Emily Heikamp, MD, PhD