KEY POINTS FOR PRACTICE
• In patients with a suspected diabetic foot infection limited to the soft tissue, culture of a soft tissue sample should be considered instead of wound swab due to higher accuracy.
• To diagnose osteomyelitis in a patient with diabetes, a combination of probe-to-bone testing, plain radiography, and ESR, CRP, or procalcitonin levels should be considered as initial tests.
• In patients with a diabetic foot infection and suspected osteomyelitis, a bone biopsy should be considered due to poor correlation of soft tissue and bone culture results.
• Urgent surgical consultation is recommended in cases of severe or moderate diabetic foot infection complicated by extensive gangrene, necrotizing infection, deep abscess, compartment syndrome, or severe lower limb ischemia.
From the AFP Editors
Diabetic foot infections are the most frequent complication of diabetes that leads to hospitalization. They are also the most common cause of lower extremity amputation. Less than one-half of infected diabetic foot ulcers heal within 1 year, and 10% of those that heal recur. The International Working Group on the Diabetic Foot (IWGDF) and Infectious Diseases Society of America (IDSA) have published guidelines on diagnosis and treatment of these infections.
CLASSIFICATION
The IWGDF/IDSA grading system for classification of diabetic foot infections should be used. This system is based on signs of localized foot inflammation and systemic inflammatory response syndrome (Table 1). For grades 3 and 4 infections, the presence of osteomyelitis is indicated by an O (ie, 3O, 4O). More recently developed classification criteria for systemic infections have not been shown to better define risk.
TABLE 1. IWGDF/IDSA Classification of Diabetic Foot Infections
| Grade | Classification | Definition |
|---|---|---|
| 1 | Uninfected | No local or systemic signs of infection |
| 2 | Mild | At least 2 signs: |
| Local swelling or induration | ||
| Erythema 0.5–2 cm from wound | ||
| Local pain or tenderness | ||
| Local increased warmth | ||
| Purulent discharge | ||
No other cause of inflammatory skin response (eg, trauma, gout, acute Charcot arthropathy, fracture, thrombosis, venous stasis) | ||
| 3 | Moderate | Infection involving: |
| Erythema extending 2 cm or more from wound | ||
| Tissue deeper than subcutaneous tissue (eg, tendon, muscle, joint) | ||
| No systemic manifestations | ||
| 3O | Moderate | Infection involves bone but no systemic manifestations |
| 4 | Severe | 2 or more systemic manifestations: |
| Temperature > 100.4°F (38°C) or < 96.8°F (36°C) | ||
| Heart rate > 90 beats/min | ||
| Respiratory rate > 20 breaths/min or Paco2 < 32 mm Hg | ||
| White blood cell count > 12,000/mm3 or > 10% immature band forms | ||
| 4O | Severe | Infection involves bone and 2 or more systemic manifestations |
IDSA = Infectious Diseases Society of America; IWGDF = International Working Group on the Diabetic Foot; Paco2 = partial pressure of carbon dioxide in arterial blood.
Adapted with permission from Senneville É, Albalawi Z, van Asten SA, et al. IWGDF/IDSA guidelines on the diagnosis and treatment of diabetes-related foot infections (IWGDF/IDSA 2023). Diabetes Metab Res Rev. 2024;40(3):e3687.
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