D. Brohee

Assessment of erythrocyte shape by flow cytometry techniques

Background: Red blood cell (RBC) rheology is altered in different diseases, including acute conditions such as patients in intensive care units (ICU) with sepsis or with an inflammatory reaction due to postoperative states or intracerebral haemorrhage, or chronic conditions such as diabetes mellitus or terminal renal failure. Several techniques are available to assess alterations in RBC rheology, especially deformability, but they are too cumbersome to be used on a large number of cells. Objective: To develop a new, rapid flow cytometry technique for easy assessment of RBC shape in patients. Methods: In flow cytometry, healthy human RBC shape shows a bimodal distribution related to the biconcave form. On this histogram, the second Pearson coefficient of dissymmetry (PCD) representing the asymmetry of this histogram and the spherical index (M2:M1) were calculated, both representing the spherical shape. This technique was used in healthy volunteers (n = 17) and in diseases characterised by abnormalities in RBC rheology, including terminal renal failure requiring haemodialysis (n = 28), diabetes mellitus (n = 18), sepsis (n = 19) and acute inflammatory states (postoperative, intracerebral haemorrhage, chronic obstructive pulmonary disease, epilepsy or severe drug intoxication; n = 21). Multivariate analysis was performed to determine the factors influencing RBC shape. Results: Measurement of RBC shape was highly reproducible. A good correlation was observed between the PCD and the spherical index, except in the critically ill patients without sepsis. RBCs were more spherical in patients with terminal renal failure (PCD −0.56 (0.14), p<0.05), diabetes mellitus (PCD −0.59 (0.23), p<0.05), sepsis (PCD −0.58 (0.22), p<0.05) or an acute inflammatory state (PCD −0.65 (0.29), p<0.05) than in healthy volunteers (PCD −0.89 (0.12)). The spherical index was also increased in all populations compared with healthy volunteers (terminal renal failure 2.30 (0.20); diabetes mellitus 2.27 (0.38); sepsis 2.28 (0.37); acute inflammatory state 2.35 (0.42) vs healthy volunteers 2.72 (0.47); all p<0.05). Multivariate analysis demonstrated that the underlying pathology (sepsis, acute inflammatory state, diabetes mellitus, terminal renal failure) was the principal cause of these RBC shape abnormalities. Conclusion: RBCs are characterised by an increased spherical shape in many disease states. The measure of the second PCD in flow cytometry is a new, easy method to investigate RBC shape in various diseases. This technique could facilitate the investigation of abnormalities of RBC rheology.

A new device for measurement of fibrin clot lysis: application to the Euglobulin Clot Lysis Time

BackgroundDetermination of clot lysis times on whole blood, diluted whole blood, plasma or plasma fraction has been used for many years to assess the overall activity of the fibrinolytic system. We designed a completely computerised semi-automatic 8-channel device for measurement and determination of fibrin clot lysis. The lysis time is evaluated by a mathematical analysis of the lysis curve and the results are expressed in minute (range: 5 to 9999). We have used this new device for Euglobulin Clot Lysis Time (ECLT) determination, which is the most common test used in laboratories to estimate plasma fibrinolytic capacity.ResultsThe correlation between ECLT and manual method is very tight : R = 0,99; p < 10-6. The efficiency scores of the method are <4% in intra-assay and <7% in inter-assay. It allows to achieve the tests on hyperlipaemic samples. This new device has been easily integrated in laboratory routine and allows to achieve several ECLT every day without disturbance of laboratory workflow.ConclusionsThe routine use of this new device could be useful in various situations such as assessment in atherosclerosis and arteriosclerosis associated diseases, coagulation survey of liver transplantations, cardiovascular surgery or pharmacological research.It has already provided highly promising results in preliminary studies on the relation between fibrinolysis and cardiovascular risk factors.

Effects of raloxifene treatment on the phenotype of blood monocytes.

Raloxifene (RLX), a selective oestrogen receptor modulator, has oestrogen-agonist effects on bone, lipoproteins, and homocysteine and oestrogen-antagonist activity in the breast and uterus, positioning it as a potential drug for long-term prevention of coronary heart disease in postmenopausal women. To further evaluate its influence on cardiovascular risk factors, we studied the effects of 60 mg/day RLX on serum lipid levels, inflammatory (high-sensitivity C-reactive protein, and coagulation (fibrinogen) markers, monocytes, and fibrinolysis in 15 healthy postmenopausal women. Markers were measured at baseline, after 1 month without treatment, and after 3 months of treatment. Fibrinolysis was evaluated using the euglobulin clot lysis time (ECLT) determined with a new semiautomatic optical method. Monocyte phenotype was determined by measurement of the expression of the antigens CD14, HLA-DR, and CD62-L using flow cytometry. After 3 months of RLX treatment, we observed a decrease in total cholesterol (p = 0.002), in low-density lipoprotein cholesterol (p <0.001), and in lipoprotein A (p = 0.01). Fibrinogen (p = 0.002) decreased significantly, and high-sensitivity C-reactive protein had a tendency to decrease, but this did not reach statistical significance (p = 0.06). RLX treatment had no effect on ECLT (p = 0.223) or on white blood cell, lymphocyte, and total monocyte counts (p = 0.313). Monocyte expression of HLA-DR, CD14, and CD62-L was not modified by the treatment. In conclusion, we confirm that RLX has beneficial short-term effects on levels of lipids and inflammatory markers, with no effect on fibrinolysis or monocyte phenotype.