Predictors of Lower-Extremity Amputation in Patients With an Infected Diabetic Foot Ulcer

TLDR

Infection commonly complicates diabetic foot ulcers and is associated with a poor outcome. The study aimed to identify independent predictors of lower‑extremity amputation, assess the prognostic value of the IWGDF classification system, and develop a risk score for predicting amputation. Prospectively, 575 patients with infected diabetic foot ulcers were enrolled from 14 clinics across 10 European countries. Among these patients, 28% underwent amputation; independent risk factors were periwound edema, foul smell, purulent exudate, deep ulcer, positive probe‑to‑bone, pretibial edema, fever, and elevated C‑reactive protein, with higher IWGDF infection severity also predicting amputation, and a newly developed risk score incorporating sex, pain on palpation, periwound edema, ulcer size, depth, and peripheral arterial disease achieved higher predictive accuracy (AUC 0.80–0.78) than the IWGDF system, though external validation is required.

Abstract

OBJECTIVE Infection commonly complicates diabetic foot ulcers and is associated with a poor outcome. In a cohort of individuals with an infected diabetic foot ulcer, we aimed to determine independent predictors of lower-extremity amputation and the predictive value for amputation of the International Working Group on the Diabetic Foot (IWGDF) classification system and to develop a risk score for predicting amputation. RESEARCH DESIGN AND METHODS We prospectively studied 575 patients with an infected diabetic foot ulcer presenting to 1 of 14 diabetic foot clinics in 10 European countries. RESULTS Among these patients, 159 (28%) underwent an amputation. Independent risk factors for amputation were as follows: periwound edema, foul smell, (non)purulent exudate, deep ulcer, positive probe-to-bone test, pretibial edema, fever, and elevated C-reactive protein. Increasing IWGDF severity of infection also independently predicted amputation. We developed a risk score for any amputation and for amputations excluding the lesser toes (including the variables sex, pain on palpation, periwound edema, ulcer size, ulcer depth, and peripheral arterial disease) that predicted amputation better than the IWGDF system (area under the ROC curves 0.80, 0.78, and 0.67, respectively). CONCLUSIONS For individuals with an infected diabetic foot ulcer, we identified independent predictors of amputation, validated the prognostic value of the IWGDF classification system, and developed a new risk score for amputation that can be readily used in daily clinical practice. Our risk score may have better prognostic accuracy than the IWGDF system, the only currently available system, but our findings need to be validated in other cohorts.