Aim: One of the greatest challenges in diabetic foot disease is estimating the impact of peripheral ischemia. Currently used non-invasive diagnostic techniques only provide rough indications. Laser Speckle Contrast Imaging (LSCI) is a promising non-invasive technique to assess microcirculation. The aim of our study was to investigate the stability, reproducibility and validity of LSCI for determination of peripheral ischemia.
Method: Thirty-three patients with diabetic foot ulcers were included in a prospective cohort study, and were classified as non-ischemic or ischemic based on international guideline criteria using ankle-brachial index (ABI), toe blood pressure and TcpO2. We performed LSCI scans of the dorsal and plantar side of the ulcerated and contralateral foot. The baseline microcirculation was determined and followed by two occlusion tests. All scans were performed twice by the principal investigator and a third time by a health professional.
Results: The intra- and inter-observer agreement were high (ICC>0.85; p<0.001, and ICC>0.7; p<0.05 respectively) for the baseline measurements and the occlusion tests. The correlation between LSCI and ABI, toe pressure and TcpO2 was weak (r=0.0–0.5). Baseline microcirculation was lower in ischemic feet compared to non-ischemic feet (40.2 vs. 51.1; non-significant), and microcirculation of the occlusion tests was significantly lower (61.9 vs. 100.8 and 34.9 vs. 66.8; p<0.05). Baseline microcirculation was significantly higher in the ulcerated foot compared to the contralateral foot (46.1 vs. 39.8; p<0.05), whereas microcirculation of the occlusion tests was insignificantly higher (82.2 vs. 74.4; 55.0 vs. 49.1).
Conclusion: LSCI is a stable, reproducible and valid technique for assessment of microcirculation in feet of people with diabetes, with high intra- and inter-observer agreement. LSCI can be useful in the determination of peripheral ischemia in diabetic foot ulcers, and is as such a promising first step towards improved diagnostics among these patients.