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Previous studies have reported correlation between the Wound, Ischemia, and foot Infection (WIfI) classification system and wound healing time on unadjusted analyses. However, in the only multivariable analysis to date, WIfI stage was not predictive of wound healing. Our aim was to examine the association between WIfI classification and wound healing after risk adjustment in patients with diabetic foot ulcers (DFUs) treated in a multidisciplinary setting.
All patients presenting to our multidisciplinary DFU clinic from June 2012 to July 2017 were enrolled in a prospective database. A Cox proportional hazards model accounting for patients’ sociodemographics, comorbidities, medication profiles, and wound characteristics was used to assess the association between WIfI classification and likelihood of wound healing at 1 year.
There were 310 DFU patients enrolled (mean age, 59.0 ± 0.7 years; 60.3% male; 60.0% black) with 709 wounds, including 32.4% WIfI stage 1, 19.9% stage 2, 25.2% stage 3, and 22.4% stage 4. Mean wound healing time increased with increasing WIfI stage (stage 1, 96.9 ± 8.3 days; stage 4, 195.1 ± 10.6 days; P < .001). Likelihood of wound healing at 1 year was 94.1% ± 2.0% for stage 1 wounds vs 67.4% ± 4.4% for stage 4 (P < .001). After risk adjustment, increasing WIfI stage was independently associated with poor wound healing (stage 4 vs stage 1: hazard ratio, [HR] 0.44; 95% confidence interval, 0.33-0.59). Peripheral artery disease (HR, 0.73), increasing wound area (HR, 0.99 per square centimeter), and longer time from wound onset to first assessment (HR, 0.97 per month) also decreased the likelihood of wound healing, whereas use of clopidogrel was protective (HR, 1.39; all, P ≤ .04). The top three predictors of poor wound healing were WIfI stage 4 (z score, -5.40), increasing wound area (z score, -3.14), and WIfI stage 3 (z score, -3.11), respectively.
Among patients with DFU, the WIfI classification system predicts wound healing at 1 year in both crude and risk-adjusted analyses. This is the first study to validate the WIfI score as an independent predictor of wound healing using multivariable analysis.