Er mean weight in the ulcer group. Earlier works have suggested an association between Title Loaded From File ulceration and BMI in diabetics [52,53]. Sickle cell disease ulceration could share a common aetiology since both conditions show similarities in several vascular complications, notably retinopathy and leg ulceration [52,54,55]. However, reports among diabetics are conflicting with observations of both positive [52] and negative [53] associations between BMI and ulceration. It is also possible that the greater BMI in the present study is related to the higher mean age in the ulcer group. The age difference between the ulcer group and patients without ulcers is consistent with findings of the role of advancing age in ulceration [4,56]. However, it is unclear how this age discrepancy may influence haemorheological determinations across groups and between genotypes. The Lightguide flow data indicated that microvascular oxygen saturation was not a precipitating factor in leg ulceration since there was no difference in the degree of tissue oxygenation in subjects with ulcers and those without. These data as determined by our definition for hypoxia Title Loaded From File appear conflicting in consideration of the lesser HVR in subjects with ulcers. However, whilst the HVR describes the efficiency of oxygen transport by RBC, it does not quantify local tissue perfusion in absolute terms. The mean SO2 values recorded along the length of the lower leg were lesser in subjects with ulcers for both the right and left leg measurements. It is likely that local hypoxia alone is not a strong indicator for the development and/or progression of leg ulcers in SCD. Mechanical injury to the endothelium by trapped rigid cells, increased number of leucocytes leading to chronic inflammation and vascular dysfunction could represent more important biomarkers in sickle cell leg ulceration. Studies have shown that the proposed `fibrin cuff’ in venous diseases do not cause a significant difference in the observed diffusion block to flowing blood between controls and subjects to implicate hypoxia in its aetiology [57]. Trapped leucocytes (by way of larger size and rigidity) in the lower leg could be a stimulus for ulceration by their damaging effects on connective tissue, cell membrane and the endothelium. Paradoxically, some authors believe that WBC in the interstitium may be targeted at fibroblasts where they promote increased cellular proliferation and fibrotic connective tissue growth and the characteristic thickened hyperpigmented skin associated with foot ulcers [57]. Furthermore, histological evidence has indicated the infiltration of the capillaries of the papillary plexus by inflammatory mediators such as monocytes, macrophages and fibrin.Other reports have likened chronic leg ulcers to a sickle cell disease sub-phenotype characterized by chronic hyperhaemolysis and a significantly lowered haemoglobin and significantly increased lactate dehydrogenase levels [4,9,58]. These contrast the present findings where we observed no differences in these variables between the ulcer group and patients without ulcers. The reasons for these differences are not clear, especially regarding conflicts among findings within the Jamaican population [4]. However, these observations suggest the presence of leg ulcers in these patients may not always be associated with more severe haemolysis than patients without ulcers. Similarities observed here between SSn and SSu could also be due to the high variation in LDH valu.Er mean weight in the ulcer group. Earlier works have suggested an association between ulceration and BMI in diabetics [52,53]. Sickle cell disease ulceration could share a common aetiology since both conditions show similarities in several vascular complications, notably retinopathy and leg ulceration [52,54,55]. However, reports among diabetics are conflicting with observations of both positive [52] and negative [53] associations between BMI and ulceration. It is also possible that the greater BMI in the present study is related to the higher mean age in the ulcer group. The age difference between the ulcer group and patients without ulcers is consistent with findings of the role of advancing age in ulceration [4,56]. However, it is unclear how this age discrepancy may influence haemorheological determinations across groups and between genotypes. The Lightguide flow data indicated that microvascular oxygen saturation was not a precipitating factor in leg ulceration since there was no difference in the degree of tissue oxygenation in subjects with ulcers and those without. These data as determined by our definition for hypoxia appear conflicting in consideration of the lesser HVR in subjects with ulcers. However, whilst the HVR describes the efficiency of oxygen transport by RBC, it does not quantify local tissue perfusion in absolute terms. The mean SO2 values recorded along the length of the lower leg were lesser in subjects with ulcers for both the right and left leg measurements. It is likely that local hypoxia alone is not a strong indicator for the development and/or progression of leg ulcers in SCD. Mechanical injury to the endothelium by trapped rigid cells, increased number of leucocytes leading to chronic inflammation and vascular dysfunction could represent more important biomarkers in sickle cell leg ulceration. Studies have shown that the proposed `fibrin cuff’ in venous diseases do not cause a significant difference in the observed diffusion block to flowing blood between controls and subjects to implicate hypoxia in its aetiology [57]. Trapped leucocytes (by way of larger size and rigidity) in the lower leg could be a stimulus for ulceration by their damaging effects on connective tissue, cell membrane and the endothelium. Paradoxically, some authors believe that WBC in the interstitium may be targeted at fibroblasts where they promote increased cellular proliferation and fibrotic connective tissue growth and the characteristic thickened hyperpigmented skin associated with foot ulcers [57]. Furthermore, histological evidence has indicated the infiltration of the capillaries of the papillary plexus by inflammatory mediators such as monocytes, macrophages and fibrin.Other reports have likened chronic leg ulcers to a sickle cell disease sub-phenotype characterized by chronic hyperhaemolysis and a significantly lowered haemoglobin and significantly increased lactate dehydrogenase levels [4,9,58]. These contrast the present findings where we observed no differences in these variables between the ulcer group and patients without ulcers. The reasons for these differences are not clear, especially regarding conflicts among findings within the Jamaican population [4]. However, these observations suggest the presence of leg ulcers in these patients may not always be associated with more severe haemolysis than patients without ulcers. Similarities observed here between SSn and SSu could also be due to the high variation in LDH valu.
