Erythrocyte Aggregation and Blood Viscosity is Similar in Homozygous Sickle Cell Disease Patients with and without Leg Ulcers.

Background There is no consensus regarding the role of red blood cell (RBC) aggregation in the pathogenesis of leg ulcers (LUs) in sickle cell disease (SCD). Objectives We sought to evaluate whether the cross-sectional determination of RBC aggregation and hematological indices were associated with the presence of LU in homozygous SCD. Methods Twenty-seven patients with LU and 23 with no history of ulceration were recruited into the study. A laser-assisted rotational red cell analyzer (LoRRca) was used in the determination of the aggregation index (AI), aggregation half-time ( t1/2 ), and the RBC aggregate strength (AMP). Hematological indices were determined using a CELL-DYN Ruby analyzer. Whole blood viscosity (WBV) and plasma viscosity (PV) were measured using a Vilastic bioprofiler. The data were presented as means ± standard deviation or median, interquartile range. Two-sample t -test was used to test for associations between the AIs, WBV, and PV in patients with and without LU. Statistical significance was taken as p < 0.05. All analyses were conducted using Stata/SE v . 12.1 (StataCorp, College Station, TX). Results The AI was comparable in the group with and without ulcers (68.6, 16.7 versus 67.7, 16.9; p = 0.74); t1/2 (1.7, 1.3 versus 1.8, 1.3; p = 0.71); AMP (18.8, 14.5 versus 19.1, 13.3; p = 0.84), WBV (3.8, 1.2 versus 3.8, 0.7; p = 0.77); and the PV (1.3, 0.08 versus 1.4, 0.1; p = 0.31) and were also not statistically different between the groups of participants. Conclusion RBC aggregation and aggregate strength are not associated with leg ulceration in SCD.

Red blood cell deformability is reduced in homozygous sickle cell disease patients with leg ulcers.

Previous reports differ as to whether a decreased elongation index (EI), a proxy for red blood cell (RBC) deformability, is associated with leg ulcers (LU) in people with homozygous sickle cell disease (SCD). We sought to determine whether erythrocyte deformability (ED) and haematological indices were associated with the presence of LU in patients with SCD. The study design was cross-sectional. Twenty-seven patients with LU and 23 with no history of ulceration were recruited into the study. A laser assisted rotational red cell analyzer was used in the determination of the EI. Haematological indices were determined using a CELL-DYN Ruby haematology analyzer. Data were normally distributed and presented as means±SD. Two-sample t-test was used to test for associations between haemorheological variables in SCD patients with and without LU. Statistical significance was taken as p < 0.05. The EI was significantly lower in the group with ulcers (0.30±0.07 vs. 0.35±0.07, p = 0.02). Haematological indices were comparable in patients with and without LU. Erythrocyte deformability, but not haematological indices, was associated with LU in patients with SCD.

Blood viscosity and the expression of inflammatory and adhesion markers in homozygous sickle cell disease subjects with chronic leg ulcers.

OBJECTIVE: To determine differences in TNF-α, IL-1ß, IL-10, sICAM-1 concentrations, leg hypoxia and whole blood viscosity (WBV) at shear rates of 46 sec(-1) and 230 sec(-1) in persons with homozygous S sickle cell disease (SCD) with and without chronic leg ulceration and in AA genotype controls. DESIGN: & METHODS: fifty-five age-matched participants were recruited into the study: 31 SS subjects without leg ulcers (SSn), 24 SS subjects with leg ulcers (SSu) and 18 AA controls. Haematological indices were measured using an AC.Tron Coulter Counter. Quantification of inflammatory, anti-inflammatory and adhesion molecules was performed by ELISA. Measurement of whole blood viscosity was done using a Wells Brookfield cone-plate viscometer. Quantification of microvascular tissue oxygenation was done by Visible Lightguide spectrophotometry. RESULTS: TNF-α and whole blood viscosity at 46 sec(-1) and 230 sec(-1) (1.75, 2.02 vs. 0.83, 1.26, p<0.05) were significantly greater in sickle cell disease subjects than in controls. There were no differences in plasma concentration of sICAM-1, IL-1ß and IL-10 between SCD subjects and controls. IL-1ß (median, IQR: 0.96, 1.7 vs. 0, 0.87; p<0.01) and sICAM-1 (226.5, 156.48 vs. 107.63, 121.5, p<0.005) were significantly greater in SSu group compared with SSn. However there were no differences in TNF-α (2, 3.98 vs. 0, 2.66) and IL-10 (13.34, 5.95 vs. 11.92, 2.99) concentrations between SSu and SSn. WBV in the SSu group at 46 sec(-1) and at 230 Sec 1 were 1.9 (95%CI; 1.2, 3.1) and 2.3 (1.2, 4.4) times greater than in the SSn group. There were no differences in the degree of tissue hypoxia as determined by lightguide spectrophotometry. CONCLUSION: Inflammatory, adhesion markers and WBV may be associated with leg ulceration in sickle cell disease by way of inflammation-mediated vasoocclusion/vasoconstriction. Impaired skin oxygenation does not appear to be associated with chronic ulcers in these subjects with sickle cell disease.