There are certain questions in our field that seem on first glance easy to solve—but simply are not. One of them being how can we better identify those febrile infants ≤ 60 days of age who do not have a serious bacterial infection and thus do not need a full sepsis evaluation when the conservative traditional approach (largely derived prior to the vaccines we now have access to) is to do an evaluation on all febrile infants in this age group. To help better predict who is and is not at risk, Aronson et al. (10.1542/peds.2018-3604) performed a case-control study of febrile infants presenting to 11 emergency departments from 2011-2016. They matched each of 181 infants studied with an invasive bacterial infection (IBI) in their blood (181) and 26 also with infected cerebrospinal fluid with two matched controls without an IBI to identify predictive factors for low risk of IBI. Using multiple logistic regression, the authors were able to identify four predictors of IBI that became incorporated into an “IBI score” including age less than 21 days (1 point), highest recorded temperature in the ED (2 points ≤ 38.4C or 4 points if greater), an absolute neutrophil count ≥ 5,185 cells/microliter (2 points), and abnormal urinalysis (3 points). This scoring system demonstrated great sensitivity with a score ≥ 2 of 98.8% but only a specificity of 31.3%.
So should you use this score proactively to determine who is at low risk for an IBI? We asked emergency medicine pediatricians Drs. Nathan Kuppermann, Prashant Mahajan, and Octavio Ramilo to share their thoughts about this score in an accompanying commentary (10.1542/peds.2019-1375). They note the great sensitivity of this score to identify those at low risk for IBI but also point out some limitations including the low specificity relative to newer algorithms that use other newer biomarkers to identify those at low and high risk for IBI. They also note that their scoring system does not take into account a viral infection like HSV which could be missed if no CSF is obtained for someone with a low score at risk for this pathogen. Since the study was retrospective, it is not clear whether assessing “well appearance” was done before or after lab tests like CSF were already known suggesting potential reporting bias. They also raise questions as to how to handle the score changing over time in the ED as temperatures get retaken and whether an admission should be automatic for someone who is not in the low-risk IBI category. They also discuss the future of biomarkers, including using gene expression with RNA biosignatures may play in predicting IBI. There is a lot of interesting information in this study and commentary—with no risk whatsoever if you check out both. In turn let us know if you use this score going forward for your febrile infants as a means of not having them experience a comprehensive sepsis evaluation as a result.