Step-by-Step Approach to Febrile Infants
Why Use
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.
When to 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 ).
Formula
Pearls / Pitfalls
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).
Management
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.
More Information
Interpretation: Risk group IBI risk Recommendation Low 0.7% Full sepsis workup likely not needed. Consider a period of ED observation, especially if the duration of fever is <2 hours, and ensure outpatient pediatrician follow-up. Intermediate 3.4% Full sepsis workup, including blood, urine, and CSF cultures, initiation of broad spectrum intravenous antibiotics, and inpatient hospital admission MAY be indicated, especially if the patient is between 21 and 28 days old. High 8.1% Full sepsis workup, including blood, urine, and CSF cultures, initiation of broad spectrum intravenous antibiotics, chest x-ray, and inpatient hospital admission are recommended.