Using AAP Guidelines for Managing Febrile Infants Without C-Reactive Protein and Procalcitonin.

Background And Objectives: In 2021, the American Academy of Pediatrics (AAP) published the Clinical Practice Guideline (CPG) for management of well-appearing, febrile infants 8 to 60 days old. For older infants, the guideline relies on several inflammatory markers, including tests not rapidly available in many settings like C-reactive protein (CRP) and procalcitonin (PCT). This study describes the performance of the AAP CPG for detecting invasive bacterial infections (IBI) without using CRP and PCT.

Methods: This retrospective cohort study included infants aged 8 to 60 days old presenting to Kaiser Permanente Northern California emergency departments between 2010 and 2019 with temperatures ≥38°C who met AAP CPG inclusion criteria and underwent complete blood counts, blood cultures, and urinalyses. Performance characteristics for detecting IBI were calculated for each age group.

Results: Among 1433 eligible infants, there were 57 (4.0%) bacteremia and 9 (0.6%) bacterial meningitis cases. Using absolute neutrophil count >5200/mm3 and temperature >38.5°C as inflammatory markers, 3 (5%) infants with IBI were misidentified. Sensitivities and specificities for detecting infants with IBIs in each age group were: 8 to 21 days: 100% (95% confidence interval [CI] 83.9%-100%) and 0% (95% CI 0%-1.4%); 22 to 28 days: 88.9% (95% CI 51.8%-99.7%) and 40.4% (95% CI 33.2%- 48.1%); and 29 to 60 days: 93.3% (95% CI 77.9%-99.2%) and 32.1% (95% CI 29.1%- 35.3%). Invasive interventions were recommended for 100% of infants aged 8 to 21 days; 58% to 100% of infants aged 22 to 28 days; and 0% to 69% of infants aged 29 to 60 days.

Conclusions: When CRP and PCT are not available, the AAP CPG detected IBI in young, febrile infants with high sensitivity but low specificity.