Signs to Diagnose Sepsis in Diabetic Foot
Sepsis in diabetic foot infection is diagnosed when the patient meets SIRS criteria (≥2 of the following): temperature >38°C or <36°C, heart rate >90 beats/min, respiratory rate >20 breaths/min, or white blood cell count >12,000/mm³ or <4,000/mm³ or >10% immature forms—in the presence of a foot infection. 1
Clinical Assessment Framework
Evaluate the patient at three levels when assessing for sepsis: 1
1. Systemic Signs (SIRS Criteria)
The presence of ≥2 of the following indicates systemic inflammatory response: 1, 2
- Temperature: >38°C or <36°C
- Heart rate: >90 beats/min
- Respiratory rate: >20 breaths/min or PaCO₂ <4.3 kPa (32 mmHg)
- White blood cell count: >12,000/mm³ or <4,000/mm³, or >10% immature (band) forms
2. Laboratory Markers of Severe Infection
Beyond SIRS criteria, additional laboratory findings suggest serious infection: 1
- C-reactive protein or procalcitonin: >2 standard deviations above upper limit of normal 1
- Uncontrolled hyperglycemia: New or worsening despite usual control 1
- Hyperlactatemia: >1 mmol/L 1
- Serum creatinine increase: >0.5 mg/dL (44 μmol/L) 1
- Coagulation abnormalities or arterial hypoxemia 1
Important caveat: Fever and elevated white blood cell count may be absent in up to half of patients with significant diabetic foot infections, so their absence does not exclude sepsis. 3
3. Local Wound Characteristics Suggesting Severe Infection
Examine the wound for features indicating deep or rapidly progressive infection: 1
- Depth: Penetration to subcutaneous tissues (fascia, tendon, muscle, joint, bone) 1
- Cellulitis extent: >2 cm from wound margin or rapidly progressive 1
- Severe local signs: Crepitus, bullae, discoloration, necrosis, gangrene, ecchymoses, petechiae, or new anesthesia 1
- Acute presentation: Rapid onset or worsening 1
4. Complicating Features
These factors increase infection severity and sepsis risk: 1
- Critical foot ischemia: Diminishes clinical findings and worsens prognosis 1
- Deep abscess or foreign body (accidental or surgical) 1
- Arterial or venous insufficiency, lymphedema 1
- Immunosuppressive illness or treatment 1
- Progression despite appropriate antibiotic therapy 1
Diagnostic Algorithm
Step 1: Obtain vital signs immediately upon presentation 1
Step 2: Perform appropriate blood tests including: 1
- Complete blood count with differential
- C-reactive protein or procalcitonin
- Blood glucose
- Serum creatinine and electrolytes
- Lactate level
- Blood cultures if systemic signs present
Step 3: Debride the wound and probe to assess depth and extent 1
Step 4: Classify infection severity using IWGDF/IDSA criteria: 1
- Grade 4 (Severe): Any foot infection WITH SIRS criteria = sepsis
- This classification directly impacts management urgency and hospitalization need
Critical Pitfalls to Avoid
- Never assume absence of fever or leukocytosis excludes sepsis—up to 50% of patients with significant infections lack these findings 3
- Do not underestimate infection severity—in one multicenter study, 42% of hospitalized diabetic foot infection patients met sepsis criteria, and clinicians undergraded severity in multiple cases 1
- Peripheral neuropathy masks pain—minimal or absent pain does not rule out severe infection in diabetic patients 3
- Foot ischemia diminishes clinical findings—vascular insufficiency can obscure signs of infection and worsen prognosis 1
Hospitalization Criteria
Immediate hospitalization is indicated for: 1
- Metabolic or hemodynamic instability (sepsis)
- Severe infection with SIRS criteria
- Need for intravenous therapy
- Critical foot ischemia
- Surgical procedures required beyond minor debridement
The presence of sepsis in diabetic foot infection carries significant mortality and morbidity risk, with unfavorable outcomes in 48% of hospitalized patients, including amputation rates of 35% during hospitalization and an additional 19% within one year. 1