Two clinicians can look at the same diabetes-related foot ulcer and describe it in completely different words. One records “plantar forefoot wound, looks superficial.” Another writes “grade 2 ulcer with mild cellulitis.” Neither description reliably tells a third clinician — or a vascular surgeon, or an auditor reviewing outcomes across a region — how serious the wound is or what is likely to happen to the limb. Standardised classification systems exist to close that gap, and the evidence of the past decade has clarified which system to reach for in which situation.
Why Classification Matters Clinically
The International Working Group on the Diabetic Foot (IWGDF) has produced evidence-based guidance on diabetes-related foot disease since 1999, and its 2019 classification guideline identified eight key factors that contribute most to clinical outcomes. These fall into three groups: patient-related (end-stage renal failure), limb-related (peripheral artery disease and loss of protective sensation), and ulcer-related (area, depth, site, single or multiple wounds, and infection). A classification system is essentially a structured way of recording those factors so that risk is not lost in narrative description (Monteiro-Soares et al., Diabetes/Metabolism Research and Reviews, 2020).
Importantly, ulcer classification is distinct from ulceration risk stratification. The IWGDF prevention guideline addresses the intact but at-risk foot, recommending annual screening for loss of protective sensation and peripheral artery disease in people at very low risk, with more frequent screening as risk category rises (Bus et al., Diabetes/Metabolism Research and Reviews, 2023). Classification systems, by contrast, describe a wound that already exists.
SINBAD: The Default for Communication and Audit
The 2023 IWGDF update was built on a systematic review that identified 28 classification systems across 149 articles, then applied GRADE methodology to match systems to clinical purposes. For communication between healthcare professionals, SINBAD — Site, Ischaemia, Neuropathy, Bacterial infection, Area, Depth — is the recommended first option. Its advantage is practical: each variable can be assessed at the bedside without specialised equipment, which makes it usable in primary care and in resource-limited settings. SINBAD is also the recommended system for auditing outcomes across local, regional, or national populations, allowing case-mix to be compared meaningfully between services (Monteiro-Soares and Game, Diabetes Therapy, 2024).
The guideline adds an important caveat that is easy to overlook: when communicating about an individual patient, the individual variables should be described rather than only a total score. A SINBAD score of 3 can arise from very different combinations of ischaemia, infection, and depth, and those combinations demand different management.
WIfI: Stratifying Amputation Risk and Revascularisation Benefit
The Wound, Ischaemia, and foot Infection (WIfI) system was developed by the Society for Vascular Surgery to grade each of those three domains separately and combine them into a clinical stage. It is recommended when the question is how well perfused the limb is and how much a patient stands to gain from revascularisation.
A systematic review and meta-analysis of 12 studies comprising 2,669 patients with chronic limb-threatening ischaemia found that estimated one-year major amputation rates rose steeply with WIfI stage: 0% for stage I, 8% for stage II, 11% for stage III, and 38% for stage IV. The authors noted that most included studies were retrospective and of moderate quality, and called for prospective evaluation — but the gradient itself is clinically meaningful prognostic information (van Reijen et al., European Journal of Vascular and Endovascular Surgery, 2019).
Infection Severity and the Limits of Prediction
For characterising an infected ulcer, the IWGDF and the Infectious Diseases Society of America jointly maintain a severity classification, updated in 2023 on the basis of 149 included studies. It grades infection from uninfected through mild, moderate, and severe, with severe infection defined by systemic inflammatory response — a distinction that drives decisions about hospitalisation, urgent surgery, and empiric antibiotic choice (Senneville et al., Clinical Infectious Diseases and Diabetes/Metabolism Research and Reviews, 2023).
One recommendation is notable for what it declines to endorse. For predicting the outcome of an ulcer in a specific individual, the 2023 guideline concluded that no existing system could be recommended. Comparative work continues: a prospective cohort of 616 ulcers in 400 patients found SINBAD and the University of Texas system performed comparably and outperformed other IWGDF-approved systems for predicting poor outcomes in an outpatient setting, with modifications to WIfI improving its performance further (Mostafavi et al., Endocrinology, Diabetes & Metabolism, 2026). These remain single-cohort findings requiring external validation.
Clinical Summary
No single classification serves every purpose. Current evidence supports SINBAD for routine communication and population-level audit, WIfI where perfusion assessment and revascularisation benefit are in question, and the IDSA/IWGDF scheme for grading infection severity. Individual prognosis remains beyond the reach of any validated system. What the literature consistently supports is the discipline of using a validated system at all — recording site, ischaemia, neuropathy, infection, area, and depth in a standardised way rather than in free text, so that severity travels intact with the patient.
References
- Monteiro-Soares M, Russell D, Boyko EJ, Jeffcoate W, Mills JL, Morbach S, Game F. Guidelines on the classification of diabetic foot ulcers (IWGDF 2019). Diabetes/Metabolism Research and Reviews. 2020;36(S1):e3273.
- Monteiro-Soares M, Game F. Podcast on How to Classify Foot Ulcers in People with Diabetes (2023 Update of the IWGDF Guidelines on Classification). Diabetes Therapy. 2024.
- van Reijen NS, Ponchant K, Ubbink DT, Koelemay MJW. The Prognostic Value of the WIfI Classification in Patients with Chronic Limb Threatening Ischaemia: A Systematic Review and Meta-Analysis. European Journal of Vascular and Endovascular Surgery. 2019;58(3):362–371.
- 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). Clinical Infectious Diseases. 2023; and Diabetes/Metabolism Research and Reviews. 2023;40(3):e3687.
- Bus SA, Sacco ICN, Monteiro-Soares M, et al. Guidelines on the prevention of foot ulcers in persons with diabetes (IWGDF 2023 update). Diabetes/Metabolism Research and Reviews. 2023;40(3):e3651.
- Schaper NC, van Netten JJ, Apelqvist J, Bus SA, Fitridge R, Game F, Monteiro-Soares M, Senneville E. Practical guidelines on the prevention and management of diabetes-related foot disease (IWGDF 2023 update). Diabetes/Metabolism Research and Reviews. 2023;40(3):e3657.
- Mostafavi F, Amini MR, Mehrabi Y, Rezvani M, Toutounchi M, Hashemi Nazari SS. Predicting Diabetic Foot Ulcer Outcomes: Machine Learning-Based Refinement of IWGDF-Approved Classifications for Outpatient Services. Endocrinology, Diabetes & Metabolism. 2026;9(3):e70193.
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