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Letters to the Editor

Blood Cultures in Cellulitis are not Cost Effective and Should Prompt Investigation for an Alternative Focus

Bryant, Penelope A. PhD; Babl, Franz E. MD; Daley, Andrew J. MBBS; Hopper, Sandy M. MBBS; Ibrahim, Laila F. MB BCH, BAO

Author Information
The Pediatric Infectious Disease Journal: January 2016 - Volume 35 - Issue 1 - p 118
doi: 10.1097/INF.0000000000000938
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To the Editors:

We read with interest the publication by Trenchs et al1 ‘Blood Cultures are not Useful in the Evaluation of Children with Uncomplicated Superficial Skin and Soft Tissue Infections’. This retrospective study showed that although 79% of patients had a blood culture, only 2 (0.6%) patients had a significant pathogen isolated. The crucial information that is not clearly stated is whether these patients were clinically different from the other patients in the study. Without this, the question remains what risk physicians are prepared to take by not taking a blood culture. The authors also did not detail whether these positive culture results affected subsequent management such as other investigations or antibiotic duration, which may be because of difficulties inherent in retrospective data collection.

We prospectively collected clinical and microbiological data on 162 patients with uncomplicated moderate/severe cellulitis (excluding complicated wounds, such as bites or containing foreign bodies, varicella and immunosuppression) receiving intravenous antibiotics. The majority—138 (85%) patients—had a blood culture. Only one (0.6%) patient had a positive culture, growing Staphylococcus aureus. He presented with 5 days of fever (38.5°C), lethargy and anorexia and 1 day of erythema and swelling over his left ankle. Difficulty with weight-bearing precipitated his hospital presentation. As data collection was prospective this culture result was deemed unusual. After 36 hours of antibiotics, he was afebrile with improving erythema, but the swelling remained. He therefore had a bone scan that showed left fibula osteomyelitis, which was treated with 3 weeks of antibiotics. He could have been differentiated at presentation from other patients with uncomplicated moderate/severe cellulitis by the prolonged history of fever. Although the positive blood culture prompted the diagnosis of osteomyelitis in this case, this would have otherwise been diagnosed based on incomplete clinical improvement. Two patients (1.2%) had blood culture contamination with coagulase-negative staphylococci, resulting in an unnecessary additional day in hospital awaiting organism identification.

The Australian Medicare Benefits Schedule cost of blood cultures (incorporating cost of consumables and scientist time for culture and sensitivities) at RCH is AU$30.75, so blood cultures in 85% of patients incurred AU$4244.2 The cost of the 2 contaminated blood cultures was 1 additional day in hospital and repeat blood culture for each patient: AU$2661, totaling AU$7284 with no clear benefit. This is excluding additional costs of medical staff drawing the culture, transportation to the laboratory, etc.

On the basis of our additional data, we agree with Trenchs et al1 that blood cultures are unhelpful in cellulitis in children and should not routinely be collected. In addition, as has previously been found in adults, they are not cost effective.3 However, we suggest that if blood cultures are obtained, positive cultures with significant pathogens are sufficiently rare that they should prompt investigation for a metastatic focus or alternative diagnosis.

Penelope A. Bryant, PhD

[email protected] Department

Infectious Diseases Unit

Department of General Medicine

Microbiology Department

Murdoch Children’s Research Institute

The Royal Children’s Hospital

Parkville, Australia

Franz E. Babl, MD

Emergency Department

Murdoch Children’s Research Institute

The Royal Children’s Hospital

Parkville, Australia

Department of Paediatrics

University of Melbourne

Melbourne, Australia

Andrew J. Daley, MBBS

Microbiology Department

The Royal Children’s Hospital

Parkville, Australia

Department of Paediatrics

University of Melbourne

Melbourne, Australia

Sandy M. Hopper, MBBS

Emergency Department

Murdoch Children’s Research Institute

The Royal Children’s Hospital

Parkville, Australia

Laila F. Ibrahim, MB BCH, BAO

[email protected] Department

Murdoch Children’s Research Institute

The Royal Children’s Hospital

Parkville, Australia

Department of Paediatrics

University of Melbourne

Melbourne, Australia

REFERENCES

1. Trenchs V, Hernandez-Bou S, Bianchi C, Arnan M, Gene A, Luaces C.. Blood cultures are not useful in the evaluation of children with uncomplicated superficial skin and soft tissue infections. Pediatr Infect Dis J. 2015;34:924–927
2. Health AGDo. MBS Online. Medicare Benefit Schedule. Available from: http://www9.health.gov.au/mbs/fullDisplay.cfm?type=item&q=69354&qt=item&criteria=bloodculture. Accessed July 19, 2015.
3. Perl B, Gottehrer NP, Raveh D, et al. Cost-effectiveness of blood cultures for adult patients with cellulitis. Clin Infect Dis. 1999;29:1483–1488
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