CLINICAL QUESTION
In patients with a diabetic foot ulcer, how likely is a lower-extremity amputation?
EVIDENCE SUMMARY
Diabetic foot ulcers are an important source of morbidity in patients with diabetes; the lifetime risk is 19% to 34% and increases with age. Diabetic foot ulcers are also an important risk factor for lower extremity amputation.1 Risk factors for developing an ulcer include comorbid kidney disease, cardiovascular disease, retinopathy, and foot deformities. Patients who use tobacco, are sedentary, or have edema or a history of ulceration are also at increased risk.1,2
Identifying patients with diabetic foot ulcer who are at the highest risk of lower extremity amputation allows physicians to prioritize intensity of care and focus on preventive efforts. Several risk scores have been proposed to assist in risk determination. The five item PEDIS (perfusion, extent, depth, infection, and sensation) risk score had very good accuracy in its derivation population but it has not been prospectively validated.3 Another risk score was developed and internally validated in 3,018 patients who were hospitalized with diabetic foot infection; of those, 21% underwent lower extremity amputation.4 However, it has not been prospectively validated in a different population or in outpatients. It also has a high data burden, with 11 items that may not be routinely available in primary care settings.
Two risk scores have been prospectively validated in outpatient settings and do not require laboratory tests. The SINBAD (site, ischemia, neuropathy, bacterial, area, depth) risk score has six items that are given 0 or 1 point. One prospective validation study found a strong association between an increase in SINBAD scores and an increase in time to healing (approximately 75 days for 0 to 1 point, 125 days for 3 to 5 points, and 577 days for 6 points).5 A French multicenter study recorded the SINBAD score for 537 outpatients who presented to a diabetic foot care clinic with a diabetic foot ulcer and followed them prospectively for 5 to 6 months. A higher score was associated with higher severity and a greater risk of lower extremity amputation. The SINBAD risk score is summarized in Table 1.5
TABLE 1. SINBAD Risk Score
| Item | Definition | Points |
|---|---|---|
| Site of ulcer | Midfoot and hindfoot | 1 |
| Forefoot | 0 | |
| Ischemia | No palpable pedal pulses | 1 |
| At least one palpable pedal pulse | 0 | |
| Neuropathy | Protective sensation absent | 1 |
| Protective sensation intact | 0 | |
| Bacterial infection | Signs of infection | 1 |
| No signs of infection | 0 | |
| Area of ulcer | ≥ 1 cm2 | 1 |
| < 1 cm2 | 0 | |
| Depth of ulcer | Reaches muscle, tendon, or deeper | 1 |
| Confined to skin and subcutaneous tissue | 0 | |
| Total score (range 0 to 6): | _______ |
Note: A minor lower extremity amputation is removal of a part of the foot distal to the transverse tarsal joint with preservation of the talus and calcaneus; a major lower extremity amputation is an above the ankle amputation.
Adapted with permission from Ince P, Abbas ZG, Lutale JK, et al. Use of the SINBAD classification system and score in comparing outcome of foot ulcer management on three continents. Diabetes Care. 2008;31(5):965.
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