C-reactive protein or erythrocyte sedimentation rate results reliably exclude invasive bacterial infections.

Background: Clinicians utilize inflammatory markers, including C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), to identify febrile children who may have an occult serious illness or infection.
Objectives: Our objective was to determine the relationship between invasive bacterial infections (IBIs) and CRP and ESR in febrile children.
Methods: We performed a retrospective cross-sectional study of 1460 febrile children <21 years of age, who presented to a single Emergency Department (ED) between 2012 and 2014 for evaluation of fever of <14 days' duration, who had both CRP and ESR obtained. Our primary outcome was IBI, defined as growth of pathogenic bacteria from a culture of cerebrospinal fluid or blood. We reviewed all ED encounters that occurred within three days of the index visits for development of IBI. We examined the negative predictive value (NPV) of CRP and ESR for IBI.
Results: Of the 1460 eligible ED encounters, the median patient age was 5.3 years [interquartile range (IQR) 2.4-10.0 years] and 762 (50.4%) were hospitalized. The median duration of fever was 4 days (IQR 1-7 days). Overall, 20 had an IBI (20/1460; 1.4%, 95% confidence interval (CI) 0.9-2.1%). None of those with a normal CRP (NPV 273/273; 100%, 95% CI 98.6-100%) or a normal ESR (NPV 486/486; 100%, 95% CI 99.2-100%) had an IBI.
Conclusions: In our cross-sectional study of febrile children, IBI was unlikely with either a normal CRP or ESR. Inflammatory markers could be used to assist clinical decision-making while awaiting results of bacterial cultures.
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