SFDI biomarkers provide a quantitative ulcer risk metric and can be used to predict diabetic foot ulcer onset

Abstract

Aims: Annually, up to 4% of people with diabetes present with a chronic foot ulcer. Quantitative real-time testing to identify patients at risk for ulceration can guide preventative care. Here, we assess whether a non-invasive optical imaging technique, Spatial Frequency Domain Imaging (SFDI), can identify patients at the highest risk for ulceration and predict ulcer onset.

Methods: We imaged 252 subjects with diabetes at Kaiser Permanente, Southern California. SFDI derived tissue biomarkers of microcirculation were compared between subjects with and without a history of ulceration, and subjects who did or did not develop ulcers after 1 year.

Results: Feet of subjects at the highest risk (i.e. history of ulceration) had significantly lower hemoglobin in the papillary dermis (HbT₁), along with higher oxygenation (StO₂) due to poor extraction. These subjects also had more homogeneous hemoglobin spread in the reticular dermis (HbT₂) and tissue scattering (related to skin structure). Prediction based on HbT₁ and tissue scattering identified new ulcerations and performed with sensitivity/specificity of 68.8%/64.8% and 75.0%/69.1%, respectively.

Conclusion: These results show that SFDI hemoglobin distribution and oxygenation biomarkers provide a quantitative basis for ulcer risk stratification and ulcer onset prediction.

Keywords: DFU; Diabetes; Non-invasive; SFDI; Ulcer risk; Vascular assessment.