All pressure ulcers are colonized with bacteria. A surface swab culture is not helpful.
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Cultures from wound surface grow colonizing organisms that are often not the real pathogens.
CDC recommends culture of fluid obtained by needle aspiration or biopsy of ulcer tissue.
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- Culture of fluid only from needle aspiration or biopsy of ulcer tissue.
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Nonhealing ulcers may have underlying osteomyelitis.
The gold standard for diagnosis of osteomyelitis is a bone biopsy.
Bone scans and plain X-rays have high false-positive and false-negative rates.
The authors of one study1 suggested using a combination of 3 tests: white blood count, erythrocyte sedimentation rate and plain X-ray.
When all three were positive, the positive predictive value was 60%
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- Consider bone biopsy to diagnose osteomyelitis.
- White blood count.
- Erythrocyte sedimentation rate.
- Plain X-ray.
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Recent studies suggest magnetic resonance imaging can differentiate bone infection from soft-tissue infection in diabetic foot infections.
MRI may be a potential diagnostic tool2, but it is an expensive and limited resource.
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References:
- Lewis LV Jr., Bailey MH, Pulawski G, et al. The diagnosis of osteomyelitis in patients with pressure sores. Plast Reconstr Surg 1988; 81(2): 229-32.
- Ferrell BA. Pressure ulcers. In Reuben DB, Yoshikawa TT, Besdine RW (eds.)
Geriatrics Review Syllabus 3rd ed. Dubuque, Iowa: Kendall/Hunt Publishing Company for the American Geriatrics Society: 1996.
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