How to Grade Diabetic Foot Ulcers
Use the IDSA/IWGDF classification system (2015 version) to grade diabetic foot infections, and consider the SINBAD system for comprehensive communication about ulcer characteristics when equipment for vascular assessment is unavailable. 1
Primary Recommendation: IDSA/IWGDF Classification for Infection
The IDSA/IWGDF system is the gold standard for grading diabetic foot infections, with four distinct grades based on clinical manifestations 1, 2:
Grade 1 (Uninfected)
Grade 2 (Mild Infection)
- Requires at least 2 of the following signs: 1, 2
- Local swelling or induration
- Erythema >0.5 cm to ≤2 cm around the ulcer
- Local tenderness or pain
- Local warmth
- Purulent discharge (thick, opaque to white or sanguineous secretion)
- Infection limited to skin and subcutaneous tissue only 1
- Critical caveat: Exclude other inflammatory causes (trauma, gout, acute Charcot neuro-osteoarthropathy, fracture, thrombosis, venous stasis) 1
Grade 3 (Moderate Infection)
- Local infection with erythema >2 cm 1, 3
- OR involvement of structures deeper than skin/subcutaneous tissue (abscess, osteomyelitis, septic arthritis, fasciitis) 1, 3
- Without systemic inflammatory response signs 1
Grade 4 (Severe Infection)
- Local infection plus systemic inflammatory response syndrome (SIRS) with ≥2 of: 1, 3
- Temperature >38°C or <36°C
- Heart rate >90 beats/min
- Respiratory rate >20 breaths/min or PaCO₂ <32 mmHg
- White blood cell count >12,000 or <4,000 cells/μL or ≥10% immature (band) forms
Secondary System: SINBAD for Comprehensive Assessment
When equipment for vascular studies is unavailable, use SINBAD as the minimum classification system for communication among healthcare professionals. 1 This system has demonstrated substantial to good reliability and requires no specialized equipment 1:
SINBAD Components (Each scored 0 or 1):
- Site: Forefoot (0) vs. Midfoot/hindfoot (1) 1
- Ischemia: At least one palpable pulse (0) vs. Clinical evidence of reduced pedal flow (1) 1
- Neuropathy: Protective sensation intact (0) vs. Lost (1) 1
- Bacterial infection: None (0) vs. Present (1) 1
- Area: Ulcer <1 cm² (0) vs. ≥1 cm² (1) 1
- Depth: Confined to skin/subcutaneous tissue (0) vs. Reaching muscle/tendon or deeper (1) 1
Total score ranges from 0-6, but report individual components, not just the total score, for adequate communication. 1
Alternative Systems (When Resources Available)
University of Texas (UT) Classification
- Uses a 4×4 matrix combining depth (Grades 0-3) and complications (Stages A-D) 1, 3
- Stage A: No infection or ischemia 3
- Stage B: Infection present 3
- Stage C: Ischemia present 3
- Stage D: Both infection and ischemia 1
- Successfully predicts complications but requires vascular assessment equipment 1
WIfI Classification (Wound, Ischemia, foot Infection)
- Consider only when vascular surgery expertise and equipment are available 1
- Combines wound grade, ischemia grade (based on ankle pressure, toe pressure, or TcPO₂), and infection grade (using IDSA/IWGDF criteria) 1
- Provides 1-year amputation risk and revascularization benefit stratification 1
- Requires ankle-brachial index measurement at minimum, limiting feasibility in resource-limited settings 1
Systems NOT Recommended
Wagner Classification
Despite being the oldest and most widely used system, Wagner classification is NOT recommended due to poor clinical discrimination 1:
- Does not individually assess area, neuropathy, infection, and peripheral arterial disease 1
- Grades 0-5 are rendered bluntly by the major impact of gangrene 1
- Most validation studies were at high risk of bias 1
Critical Caveat for Prognosis
Do not use any currently available classification system to predict individual patient outcomes. 1 The evidence quality for predicting ulcer-related outcomes is weak, with likelihood ratios indicating only small changes in pre- to post-test probability 1. Classification systems should be used for communication and treatment guidance, not for offering individual prognosis 1.