Denis F Noubouossie

Thrombin generation reveals high procoagulant potential in the plasma of sickle cell disease children.

Changes in several components of the clotting system are well documented in sickle cell disease (SCD) patients. However, whether the global hemostatic potential of these patients is altered is still unclear. Calibrated automated thrombogram® method of thrombin generation (TG) was used to characterize the hemostatic potential of 83 SCD children (75 SS, 6 SC, and 2 Sβ thal) at steady‐state as compared with 50 controls of the same range of age. TG was triggered using 1 pM tissue factor and 4 μM phospholipids with and without thrombomodulin. Thirteen SCD children were also evaluated during vaso‐occlusive crisis. Protein C activity, free protein S and D‐dimers levels were measured in parallel. SCD patients showed higher rates of thrombin formation, higher thrombin peak height (with and without thrombomodulin), and higher endogenous thrombin potential (ETP) than controls in the presence of thrombomodulin. Reduction of ETP (RETP) in the presence of thrombomodulin was lower in SCD group compared with controls and correlated both with protein C and protein S levels. ETP, RETP, peak height, and velocity index of TG correlated with D‐dimers. Compound heterozygous patients showed an intermediate hemostatic phenotype at steady‐state. No significant difference was observed when comparing TG parameters during vaso‐occlusive crisis to those obtained at steady‐state in the same patients. The global hemostatic potential is increased and reflects the hypercoagulable state of SCD patients even at steady‐state. The relevance of this finding with respect to the risk of thrombotic complications of the disease needs further investigation. Am. J. Hematol. 2011.

Evaluation of the procoagulant activity of endogenous phospholipids in the platelet-free plasma of children with sickle cell disease using functional assays.

BACKGROUND The mechanisms of hypercoagulability in sickle cell disease (SCD) are poorly understood. OBJECTIVE We aimed to explore the procoagulant activity of endogenous phospholipids (ePL) in the platelet-free plasma of SCD children. METHODS A factor Xa clotting time (XACT), thrombin generation (TG) and a capture-based assay for the detection of procoagulant microparticles (PMP) were used. Forty three SCD children (35 SS, 6 SC and 2 Sβ+) were evaluated at steady-state and compared to 20 controls. Fourteen patients were also evaluated during vaso-occlusive crisis. TG was performed using 10 pM tissue factor without addition of exogenous phospholipids. A control condition was also performed using 10 pM tissue factor and 4 μM phospholipids. Percentages of the test/control conditions were calculated for the peak height (% peak), endogenous thrombin potential (% ETP) and velocity index (% VI). RESULTS XACT times were shorter, PMP levels, peak height and velocity index of thrombin generation were higher in SCD patients than controls. Lag time and ETP were not different between the two groups. % peak, % ETP and % VI were higher in patients than controls. Significant correlations were found between PMP levels and XACT, also between PMP levels and peak height, velocity index, ETP and their respective percentages to the control condition, but not with lag time. Double heterozygous patients showed intermediate values for XACT and TG parameters. No significant difference was observed when comparing patients at steady-state versus vaso-occlusive crisis. CONCLUSION High procoagulant activity of ePL was observed in the platelet-free plasma of SCD children, probably borne by procoagulant microparticles. This may contribute to a high hemostatic potential and predisposition to thrombotic complications in these patients.

Thrombin generation in children with sickle cell disease: relationship with age, hemolysis, transcranial doppler velocity, and hydroxyurea treatment.

Increased thrombin generation (TG) was described in sickle cell disease (SCD) children. The aim of this study was to characterize TG at the individual level and assess its relationship with age, hemolysis, transcranial Doppler velocity (TCD), and hydroxyurea treatment.

Reduction of the Six-Minute Walk Distance in Children with Sickle Cell Disease Is Correlated with Silent Infarct: Results from a Cross-Sectional Evaluation in a Single Center in Belgium

Background The 6-minute walk test (6MWT) is used in adults and children affected by a wide range of chronic diseases to evaluate their sub-maximal exercise capacity. It reflects the global response of various physiological systems in a situation simulating a daily life activity. Methods We analyzed factors affecting the 6MWT in 46 Sickle Cell Disease children. Forty-two were treated with hydroxyurea (HU). Patients with normal test (>80% of the age-standardized predicted value) were compared to patients with abnormal test (≤80%). Baseline hematological values, clinical events, cerebrovascular disease, cardio-pulmonary parameters and disease-modifying treatment were compared according to the performance of the test. Results Among the 46 patients, 14 had an abnormal 6MWT. In univariate analysis, both groups were similar for biological and clinical data. Six of the 14 patients with an abnormal 6MWT had silent infarct (SI) compared to 6/32 with a normal test (P = 0.09). When excluding chronically transfused patients, 4 of the 11 patients with an abnormal 6MWT had SI compared to 1/26 (P = 0.02). Baseline pulse oximetry was normal in both groups but slightly lower in patients with abnormal 6MWT (P = 0.02). No patient presented exercise-induced desaturation. In multivariate analysis, the only factor associated with abnormal 6MWT was the presence of SI (P = 0.045). Conclusions In our cohort of 46 patients characterized by high exposure rate to HU and by the absence of severe cardiopulmonary disease, the sole factor independently associated with 6MWT was the presence of SI. The lower exercise capacity of children with SI may reflect some subclinical neurological impairment as they do not differ by hemoglobin level or cardiopulmonary parameters.

An automated chemiluminescence immunoassay may detect mostly relevant IgG anticardiolipin antibodies according to revised Sydney criteria.

Abstract Background: Detection of anticardiolipin antibodies (ACA) is an independent laboratory criterion for diagnosis of antiphospholipid syndrome (APS). Alternative methods to ELISA were recently developed such as automated chemiluminescence immunoassay (CLIA). Patients and methods: We compared a CLIA to an ELISA kit for the detection of IgG isotype of ACA. 87 routine samples from 75 patients suspected of having APS were tested using each method. Cut-off values were calculated in our laboratory for each test using 99th percentile of 50 normal controls. Results: Cut-off values were > 20 GPL for ELISA and > 2 GPL for CLIA. Overall agreement (OA), agreement for positive (AP) and agreement for negative (AN) cases were 56.3%, 49.2% and 77.2% respectively. Most discrepant results were positive with ELISA and negative with CLIA. However, OA, AP and AN increased to 82.1%, 84.6% and 80% respectively when CLIA was compared to the repeated ELISA performed at least 12 weeks later. When correlated with APS-related clinical background, CLIA showed lower sensitivity, higher specificity and higher likelihood ratio (LR) as compared to first ELISA whereas these parameters were similar to those of the repeated ELISA. No association was found between any test results and APS-related clinical background of the patients. Using our own cut-off value (> 2GPL), sensitivity, specificity and LR of CLIA to identify patients with APS were respectively 100%, 72.3% and 3.6. A ROC curve showed that at 7.5 GPL cut-off value, specificity and LR improved to 91.1% and 11.25 respectively, without affecting sensitivity. A strong correlation was observed between CLIA results and APS (χ2 = 12.25; p < 0.001). Conclusion: The performance of CLIA is as good as a repeated ELISA test to detect IgG ACA in suspected APS patients. It is fully automated, which represents several advantages over semi-manual ELISA techniques for its implementation in a routine laboratory.

Different profile of thrombin generation in children with acute lymphoblastic leukaemia treated with native or pegylated asparaginase: A cohort study

Asparaginase (Asp) and corticosteroid (CS) treatment in patients with acute lymphoblastic leukaemia (ALL) is associated with an increased risk of thrombotic events.

Management of Refractory Essential Thrombocythemia With Anagrelide in a Patient Undergoing Hemodialysis

BACKGROUND Management of essential thrombocythemia (ET) in high-risk patients is difficult because high platelet numbers can lead to vascular occlusive events and bleeding. Therapeutic interventions in ET are limited to hydroxyurea and anagrelide; however, in Europe, anagrelide is contraindicated in patients with chronic renal disease. OBJECTIVE The aim of this case report was to describe the use of anagrelide in a patient with ET and renal impairment. CASE SUMMARY A 73-year-old white female patient with severe renal impairment who was diagnosed with ET was receiving treatment with hydroxyurea 1 g/d since 2001. At this time she was also receiving aspirin 80 mg/d; calcium carbonate 1 g/d; pravastatin 40 mg/d; folic acid 5 mg/d; furosemide 40 mg/d; cetirizine 10 mg/d; erythropoietin 10,000 U once monthly; a vitamin B complex, 1 tablet a day; and iron tablets 105 mg/d. In February 2007, because her white blood cell count fell to 2.1 x 10(9)/L, myelodepression was suspected and hydroxyurea was stopped. This led to enhanced platelet levels and the introduction of anagrelide at an initial dose of 0.5 mg/d that was steadily increased to 2.5 mg/d. All other treatments were continued with some dosage adjustments. Sodium bicarbonate 1 g/d and vitamin D were added to her regimen. After 18 months of anagrelide treatment, a sudden but moderate fall of platelets to 142 x 10(3)/microL with severe anemia (hemoglobin, 6.5 g/dL) was observed. The patient had anemia since 2004, but the condition worsened due to bleeding related to an ulcer at the cecal valve. The patient refused blood and platelet transfusions and surgical intervention for religious reasons. Because of hemodynamic instability, she was admitted to the intensive care unit in December 2008 and died 24 hours after admission. CONCLUSION We report a case of ET and chronic renal failure treated with anagrelide and low-dose aspirin in a patient who did not receive transfusion and surgical intervention due to religious reasons, and had a fatal outcome.

Effective tranexamic acid concentration for 95% inhibition of tissue-type plasminogen activator induced hyperfibrinolysis in children with congenital heart disease: A prospective, controlled, in-vitro study.

BACKGROUND Although recent studies have assessed tranexamic acid (TXA) pharmacokinetics in different subgroups, the effective concentration of TXA required to completely inhibit fibrinolysis remains to be determined. OBJECTIVE An in-vitro determination of the effective TXA concentration needed for 95% inhibition (EC95) of tissue-type plasminogen activator (t-PA) activated fibrinolysis, using an experimental model designed for thromboelastometry (ROTEM). DESIGN A prospective interventional study. SETTING Department of Anaesthesiology, Queen Fabiola Childrens University Hospital and Laboratory of Haematology and Haemostasis, Brugmann University Hospital. Patients were enrolled between June 2013 and October 2014. PATIENTS AND VOLUNTEERS Twenty children, aged between 1 and 10 years, undergoing elective cardiac catheterisation were included (10 with cyanotic and 10 with noncyanotic diseases). Exclusion criteria were child requiring a procedure in a moribund state. Ten adult volunteers were also included as controls. INTERVENTION Citrated whole blood samples were obtained from children and volunteers. MAIN OUTCOMES MEASURES The extrinsic coagulation pathway was activated by tissue factor using the EXTEM test on ROTEM. The degree of lysis measured 30 min (LI30) after the clotting time (CT), and clot amplitudes measured at different times were recorded at baseline, after addition of 1535 units t-PA ml−1, and following the addition of increasing TXA concentrations in t-PA activated samples. RESULTS The concentration-effect analysis performed with lysis index after 30 min (LI30) allowed the determination of TXA efficacy concentration 50% (EC50), and calculation of the EC95, which was significantly lower in cardiac surgery children than in adults [8.6 &mgr;g ml−1; 95% confidence interval (95% CI) 6.9 to 14.9 versus 11.3 &mgr;g ml−1; 95% CI 10.6 to 12.9, P < 0.001]. CONCLUSION In this in-vitro study, we observed that the EC95 TXA concentration that completely inhibited t-PA induced hyperfibrinolysis in children with congenital heart was significantly lower than the concentration required in healthy adult volunteers. Further studies are needed to confirm that this plasma concentration can effectively inhibit fibrinolysis activation in children undergoing cardiac surgery.