Ratio of Perfusion in the Skin of the Index Finger and Big Toe in Patients with Type 2 Diabetes Mellitus

Abstract The aim of this study was to investigate the ratio of baseline perfusion levels in the skin of the palmar surfaces of the fingers and plantar surfaces of the big toe in healthy volunteers and patients with diabetes mellitus. Three study groups were included: healthy volunteers (group 1, n = 29), patients with type 2 diabetes mellitus (DM2) without diabetic foot syndrome (group 2, n = 27), and patients with diabetic foot syndrome (group 3, n = 27). All subjects were measured for the level of perfusion in the skin of the upper and lower extremities using the method of incoherent optical fluctuation flowmetry (IOFF). Perfusion was assessed in perfusion units (p.u.). The measurement was carried out sequentially, first on the left side of the body, then on the right. The baseline perfusion values from the index finger of the hand (BPh) and from the big toe of the foot (BPf) in perfusion units (p.u.) were assessed at rest. The BPh value in group 1 was 11.5 [5.4; 16.8] p.u.; in group 2, 17.4 [13.2; 24.8] p.u.; in group 3, 18.4 [13.2; 23.6] p.u. The BPh level was statistically significantly lower in group 1 than in groups 2 (p1–2 < 0.001) and 3 (p1–3 < 0.001). There was no statistically significant difference in finger perfusion between groups 2 and 3 (p2–3 = 1). The BPf values in groups 1, 2, and 3 were 4.4 [2.3; 8.8], 7.9 [5.4; 14.6], and 3.9 [1; 9.9] p.u., respectively. The BPf level in group 2 was higher than in group 1 (p1–2 = 0.006), but the parameter in group 3 was comparable to the values from group 1 (p1–3 = 0.73) and different from group 2 (p2–3 < 0.001). Thus, in group 3, there was a pseudonormalization of this index due to abnormally low BPf values in the extremities with hemodynamically significant stenoses. The baseline perfusion ratio (BPh/BPf) in groups 1, 2, and 3 was 2.11 [1.22; 3.03], 1.91 [1.18; 3.92], and 4.29 [1.8; 12.84], respectively. The BPh/BPf ratio in group 3 was significantly higher than in groups 1 (p1–3 < 0.001) and 2 (p2–3 < 0.001). The ability to detect the presence of hemodynamically significant lower limb arterial stenoses was analyzed by the BPf and BPh/BPf indices; the area under the ROC curve for BPf was 0.808 (0.729; 0.887); for BPh/BPf, 0.855 (0.782; 0.928). It was shown that an increase in the BPh/BPf ratio to exceed 3.7 with a sensitivity of 75.7% and a specificity of 81.4% indicates the presence of hemodynamically significant stenoses according to the ROC analysis. The presence of arterial blood flow abnormalities in the great arteries of the lower extremities leads to a significant reduction in BPf level. Calculation of the BPh/BPf ratio is more informative in identifying limbs with hemodynamically significant stenoses than the BPf level and can be used as a screening method for identifying patients with lower limb arterial disease.