Study Validates SVS WIfI Classification System to Predict Wound Healing in Diabetic Foot Ulcers

April 12, 2018—Caitlin W. Hicks, MD, et al published findings from the first study to validate the Society for Vascular Surgery's Wound, Ischemia, and foot Infection (WIfI) classification system as an independent predictor of wound healing in diabetic foot ulcers (DFUs) using multivariable analysis. The study is available online in Journal of Vascular Surgery (JVS).

According to the investigators, previous studies have reported a correlation between the 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. The investigators’ aim was to examine the association between WIfI classification and wound healing after risk adjustment in patients with DFUs treated in a multidisciplinary setting.

All patients presenting to the investigators' 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 the likelihood of wound healing at 1 year.

As summarized in JVS, there were 310 DFU patients enrolled (mean age, 59 ± 0.7 years; 60.3% men; 60% African Americans) 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 higher WIfI stage (stage 1, 96.9 ± 8.3 days; stage 4, 195.1 ± 10.6 days; P < .001). The likelihood of wound healing at 1 year was 94.1% ± 2% for stage 1 wounds versus 67.4% ± 4.4% for stage 4 (P < .001).

The investigators reported that after risk adjustment, a higher 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 cm²), 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), greater wound area (z score, -3.14), and WIfI stage 3 (z score, -3.11), respectively.

Among patients with DFUs, the WIfI classification system predicts wound healing at 1 year in both crude and risk-adjusted analyses, concluded the investigators in JVS. They advised that this is the first study to validate the WIfI score as an independent predictor of wound healing using multivariable analysis.