Blood Cultures in the Emergency Department Evaluation of Childhood Pneumonia

Samir S. Shah, MD, MSCE; Maria H. Dugan, BA; Louis M. Bell, MD; Robert W. Grundmeier, MD; Todd A. Florin, MD; Elizabeth M. Hines, BA; Joshua P. Metlay, MD, PhD

Disclosures

Pediatr Infect Dis J. 2011;30(6):475-479. 

In This Article

Abstract and Introduction

Abstract

Background: Blood cultures are frequently obtained in the emergency department (ED) evaluation of children with community-acquired pneumonia (CAP).
Objectives: To determine the prevalence of bacteremia in children presenting to the ED with CAP, identify subgroups at increased risk for bacteremia, and quantify the effect of positive blood cultures on management.
Methods: This case–control study was nested within a cohort of children followed up at 35 pediatric practices. Patients from this cohort who were ≤18 years of age, evaluated in the ED in 2006–2007, and diagnosed with CAP were eligible. Cases were those with bacteremia. Controls included those with negative blood cultures and those without blood cultures performed.
Results: A total of 877 (9.6%) of 9099 children with CAP were evaluated in the ED. The mean age was 3.6 years; 53% were male. Blood cultures were obtained from 291 children (33.2%). Overall, the prevalence of bacteremia was 2.1% (95% confidence interval [CI]: 0.8%–4.4%). Bacteremia occurred in 2.6% (95% CI: 1.0%–5.6%) with an infiltrate on chest radiograph and in 13.0% (95% CI: 2.8%–33.6%) with complicated pneumonia. Streptococcus pneumoniae accounted for 4 of the 6 cases of bacteremia. Blood culture results altered management in 5 of the 6 bacteremic patients; 1 had an appropriate broadening and 4 had an appropriate narrowing of coverage. The contamination rate was 1.0% (95% CI: 0.2%–3.0%).
Conclusion: Children presenting to the ED for evaluation of CAP are at low-risk for bacteremia. Although positive blood cultures frequently altered clinical management, the overall impact was small because of the low prevalence of bacteremia.

Introduction

Blood cultures are frequently obtained in the diagnostic evaluation of children presenting with community-acquired pneumonia (CAP) to the emergency department (ED). Previous studies reported low rates of bacteremia in children with pneumonia evaluated in the ED with rates ranging from 1.2% to 2.7%.[1–4] However, these studies were performed before widespread use of the heptavalent pneumococcal conjugate[1–4] and the Haemophilus influenzae type b vaccines.[2,4] Given the changing epidemiology of childhood pneumonia, the current risk of bacteremia in children evaluated in the ED is unknown.

Blood cultures are not recommended as part of the routine evaluation of adults presenting with CAP to the ED.[5] The decision to perform blood cultures in children evaluated in the ED setting is controversial because few studies have quantified the effect of positive blood cultures on clinical decision-making. Potential advantages of obtaining blood cultures include identification of a causative bacterium, which may allow clinicians to narrow or broaden antibiotic therapy. Potential disadvantages stem from the possibility of a false-positive blood culture result, which may lead to unnecessary diagnostic tests and treatments, or prolonged hospitalization.

Studies of CAP in the adult population conclude that positive blood cultures rarely alter clinical management.[6–9] Data on the utility of blood cultures in the treatment of childhood pneumonia are limited. Hickey et al[1] found no change in clinical management in 11 children with pneumonia whose blood cultures were positive for pathogenic bacteria. The effect of contaminant blood cultures was not investigated in this study. Other pediatric studies examined the role of blood cultures in the ED[10] and, more specifically, in the management of cellulitis[11] and fever.[12–14] These studies reported contamination rates ranging from 0.8% to 7.3%. The 2 studies in this group conducted after licensure of the heptavalent pneumococcal conjugate vaccine found that the proportion of contaminant bacteria exceeded the proportion of pathogenic bacteria in a ratio greater than 3:1.[10,13] Changes in clinical management occurred in fewer than half of the patients with positive blood cultures.[10] Among children with cellulitis, the most common intervention was an additional blood culture obtained to document resolution of bacteremia.[11]

The objectives of this study were to determine the prevalence of bacteremia in children presenting with CAP to the ED, identify subgroups at increased risk for bacteremia, and quantify the implications of positive blood cultures on clinical management.

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