Reassessing the performance of the “step-by-step” approach to febrile infants aged 90 days and younger in the context of the COVID-19 pandemic: a multicentric retrospective study

Abstract BackgroundInfants with COVID-19 can often present with fever without source which is a challenging situation in infants < 90 days old. The “step-by-step” algorithm has been proposed to identify children at high risk of bacterial infection. In the context of the COVID-19 pandemic, we aimed to reassess the diagnostic performance of this algorithm.MethodsWe performed a multicentric retrospective study in 3 French pediatric emergency departments between 2018 and 2020. We applied the “step-by-step” algorithm to four clinical entities: COVID-19, febrile urinary tract infections (FUTI), invasive bacterial infection (IBI), and enterovirus infections. The main outcome was the proportion of infants classified at high risk.ResultsAmong the 199 infants included, 40 had isolated COVID-19, 25 had IBI, 60 had FUTI, and 74 had enterovirus infection. All but one infant with bacterial infection were classified at high risk (96% for IBI and 100% for FUTI) as well as 95% with enterovirus and 82% with COVID-19. Infants with COVID-19 were classified at high risk because an ill appearance (72%), an age ≤ 21 days (27%) and/or leukocyturia (19%). All these infants had procalcitonin values 20 mg/L.ConclusionsThe “step-by-step” algorithm remains effective to identify infants with bacterial infection but misclassifies most infants with COVID-19 as at high risk of bacterial infection leading to unnecessary cares. An updated algorithm based adding viral testing may be needed to discriminate fever related to isolated COVID-19 in infants < 90 days old.