Things We Do For No Reason: Blood Cultures for Uncomplicated Skin and Soft Tissue Infections in Children
Skin and soft tissue infections (SSTIs) are common pediatric diagnoses in both outpatient and inpatient settings. Blood cultures are frequently obtained for evaluation of SSTIs. Multiple studies have demonstrated that blood cultures rarely demonstrate true pathogenic bacterial growth, and even positive cultures do not change clinical management. Obtaining blood cultures has been associated with increased length of hospital stay. In addition, false-positive blood cultures may occur and result in repeat blood cultures and increased hospital charges. Clinicians should avoid obtaining blood cultures in pediatric patients with uncomplicated SSTIs but instead should focus on obtaining wound cultures when possible.
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Harms Associated With Unnecessary Blood Cultures in SSTIs
Blood cultures necessitate venipunctures, which are painful for children and families. The inevitable false-positive contaminants also lead to repeat venipunctures and, potentially, unnecessary antibiotic exposure. From a high-value care perspective, Parikh et al reported hospital charges of $300 per blood culture and $250 for identification and sensitivity of positives.6 Assuming that these single-center charges are representative of national charges and using 0.5% true positivity and 1.5% false positivity rates, subjecting all children with uncomplicated SSTIs to blood culture would result in $60,250 charges to find one true positive blood culture, with no resultant changes in management. Additionally, among the 200 children cultured to find one true positive, there would be 3 false positives, necessitating another $1650 in charges for identification, sensitivity analysis, and repeat culture. These amounts do not factor in the significant expenditures associated with increased LOS. The potential savings associated with forgoing blood cultures in children with SSTIs should be an incentive for institutional change.
When Blood Cultures May Be Reasonable
The current IDSA guidelines recommend blood cultures for SSTIs in patients with immunodeficiency, animal bites, and immersion injuries (soft tissue injuries occurring in fresh or saltwater).12 Previous studies also delineated criteria for “complicated” SSTIs, typically defined as surgical or traumatic wounds, infections requiring surgical intervention (not including simple incision and drainage), or infected ulcers or burns.8,9 In the study of Malone et al, 10 (12.5%) positives were found among 80 patients with complicated SSTIs who had blood cultures performed.8 Although this work had a single-center study design with a relatively small sample size, no unusual organisms were found; the grown cultures included MRSA, MSSA, and S. pneumoniae. In addition to patients with complicated SSTIs, immunocompromised children, such as those receiving chemotherapy or other immunosuppressive agents, were excluded from the studies of blood culture yield in SSTIs and may warrant blood cultures given the risk of overwhelming infection and susceptibility to rare or invasive organisms.12 In a study of 57 pediatric patients with leukemia and no central catheters who experienced skin or soft tissue complications, Demircioglu et al13 reported 6 positive blood cultures, including Klebsiella oxytoca, Pseudomonas aeruginosa, and Escherichia coli. These organisms would not be covered by typical SSTI antibiotic regimens, illustrating the value of blood cultures in this selected group of patients. Lastly, although the above studies included some infants, the data on utility of blood cultures in neonates are limited. Blood cultures may be reasonable in this group given the relative immunocompromised state of neonates compared with older children. Additionally, any infants aged
What You Should Do Instead Of Blood Cultures for Uncomplicated SSTIs
Gram stain and wound culture of any purulent material may assist with choice of empiric antibiotic therapy and appropriate narrowing of regimen for antibiotic stewardship. Wound cultures of purulent material can identify the causative organism in 58%-66% of the cases.9,14 The rate of wound culture varies widely from 29% to 81% in studies across different healthcare systems.9,10,15 The use of visually appealing posters advising clinicians to “culture pus, not blood” has been shown to significantly decreased the number of blood cultures performed at a single pediatric hospital.10
RECOMMENDATIONS
- Do not obtain blood cultures in pediatric patients with uncomplicated SSTIs.
- If purulent material is available spontaneously or after incision and drainage, then send it for Gram stain and bacterial culture.
- Blood cultures are reasonable in patients with complicated SSTIs and in immunocompromised patients with SSTIs.
- Despite limited data, blood cultures may be reasonable in neonates with SSTIs. Febrile infants with SSTIs aged less than 90 days should be managed under existing febrile infant guidelines.
CONCLUSIONS
Blood cultures in pediatric patients with uncomplicated SSTIs have no proven benefit and are associated with increased LOS, non-negligible false-positive rate, and associated increase in financial charges to the patient and healthcare system. The patient described in the clinical scenario would have an extremely low likelihood of having any meaningful clinical information provided by blood culture as part of her evaluation.
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DISCLOSURES
The authors have no conflicts of interest relevant to this article to disclose.
