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ABSTRACT: Venous thromboembolism (VTE) has been reported to be less common among Thais than Caucasians. Whether this observation reflects genetic or environmental factors, or both, is uncertain. To identify genetic and acquired risk factors of Thai patients with VTE, we enrolled in the study 105 consecutive Thai patients (34 men, 71 women) who had an objectively confirmed history of VTE. A complete clinical summary was obtained from each patient, with emphasis on personal and family history of VTE, as well as circumstantial vascular risk factors (surgery, immobilization, pregnancy, postpartum condition, trauma, oral contraceptive use, and malignancy). Of the 105 patients, 19% were found to have a malignancy. The mean age at the time of the first thrombotic episode was 52.1 years (range, 29-76 years), compared with 42.6 years (range, 17-82 years) for the patients without malignancy. Of the 85 patients without malignancy, 12.3% had protein S deficiency, 8.9% had protein C deficiency, 4.7% had antithrombin deficiency, 10.4% had antiphospholipid antibody, 30.4% had an elevated factor VIII level, 26.8% had an elevated factor XI level, 5.3% had hyperhomocysteinemia, and 16.5% were on oral contraceptives before the thrombotic episode. Factor V Leiden, the G20210A prothrombin gene mutation, and homozygosity for the C677T methylenetetrahydrofolate reductase (MTHFR) gene variant were not found. The VTE in 7.1% of the patients was considered to be secondary to recent surgery, trauma, and/or immobilization. Compared with studies of Caucasian patients, there were significant differences in the risk factors for VTE, with protein S deficiency and protein C deficiency being more common in the Thai patients. In contrast, factor V Leiden, the G20210A prothrombin gene mutation, and the C677T MTHFR gene mutation are not genetic risk factors among Thai patients with VTE. Malignancy and the use of oral contraceptives were the most common acquired risk factors for VTE in the Thai patients.
International Journal of Hematology 01/2008; 86(5):397-402. · 1.27 Impact Factor
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ABSTRACT: Increased frequency of thrombosis has been observed in patients with hemoglobin E/beta-thalassemia (Hb E/beta-thal) disease, particularly those who have previously been splenectomized. We compared various hemostatic and thrombotic markers in blood from 15 Hb E/beta-thal patients who were not splenectomized (NS), 15 who had been splenectomized (S), and 15 normal controls (NC). Levels of plasma thrombin-antithrombin, beta2 thromboglobulin, C-reactive protein, tissue plasminogen activator antigen were significantly higher in the S group than in either the NS or the NC groups, and levels of prothrombin fragment 1.2 were significantly higher in the S than in the NC group. Levels of plasminogen activator inhibitor-1 antigen were significantly higher in the S than in the NS group. Levels of protein C, protein S, antithrombin, and fibrinogen were significantly lower in the S and NS groups than in the NC group. Plasma lipoprotein(a) levels in the S and NS groups were not statistically different from NC. Our findings indicated that there is evidence of chronic low-grade coagulation and platelet activation, chronic low-grade inflammation, endothelial cell injury, impaired fibrinolysis, and decreased naturally occurring anticoagulants in splenectomized Hb E/beta-thal patients. These changes may account for the increased risk of thrombosis in these patients.
American Journal of Hematology 12/2007; 82(11):1001-4. · 4.67 Impact Factor
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ABSTRACT: Increased frequency of thrombosis has been observed in patients with hemoglobin E/β-thalassemia (Hb E/β-thal) disease, particularly those who have previously been splenectomized. We compared various hemostatic and thrombotic markers in blood from 15 Hb E/β-thal patients who were not splenectomized (NS), 15 who had been splenectomized (S), and 15 normal controls (NC). Levels of plasma thrombin-antithrombin, β2 thromboglobulin, C-reactive protein, tissue plasminogen activator antigen were significantly higher in the S group than in either the NS or the NC groups, and levels of prothrombin fragment 1.2 were significantly higher in the S than in the NC group. Levels of plasminogen activator inhibitor-1 antigen were significantly higher in the S than in the NS group. Levels of protein C, protein S, antithrombin, and fibrinogen were significantly lower in the S and NS groups than in the NC group. Plasma lipoprotein(a) levels in the S and NS groups were not statistically different from NC. Our findings indicated that there is evidence of chronic low-grade coagulation and platelet activation, chronic low-grade inflammation, endothelial cell injury, impaired fibrinolysis, and decreased naturally occurring anticoagulants in splenectomized Hb E/β-thal patients. These changes may account for the increased risk of thrombosis in these patients. Am. J. Hematol., 2007. © 2007 Wiley-Liss, Inc.
American Journal of Hematology 07/2007; 82(11):1001 - 1004. · 4.67 Impact Factor
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ABSTRACT: Chronic transfusion of packed red blood cells, in addition to other ongoing treatment with warfarin, acetyl salicylic acid, desferrioxamine, and other supportive measures, was given to a splenectomized hemoglobin E/beta-thalassemia woman with pulmonary arterial hypertension (PHT). Serial measurements of plasma thrombin-antithrombin III complex (TAT) levels and right-sided cardiac catheterization were used to monitor changes after treatment. Reduction of plasma TAT levels from 7.5 to 3.8 microg/L (normal, 3 +/- 2.4 microg/L), pulmonary vascular resistance (PVR) from 553.8 to 238.6 dyne.sec.cm(-5) (normal, 67 +/- 30 dyne.sec.cm(-5)), and mean pulmonary arterial pressure from 51 to 32 mm Hg (normal, 9 to 19 mm Hg) occurred in tandem. Normalization of blood hypercoagulability as reflected in plasma TAT level by chronic blood transfusion was the likely basis for improvement of increased PVR, being secondary to thrombotic pulmonary arteriopathy and subsequently PHT.
Blood 05/2004; 103(7):2844-6. · 9.90 Impact Factor
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ABSTRACT: Our aim was to study the cause and describe the clinical features of pulmonary arterial hypertension (PHT) in splenectomized beta-thalassemia (beta-Thal) patients. Ten splenectomized beta-Thal patients with systolic pulmonary artery (PA) pressure >30 mm Hg were evaluated by echocardiography, right-heart catheterization, and pulmonary angiography. Five of these patients later underwent hemodynamic studies. Echocardiography and pulmonary angiography on the 10 patients showed normal values of left ventricular systolic function and no findings of acute or chronic pulmonary embolism. Hemodynamic evaluation showed very high PA pressures associated with markedly increased pulmonary vascular resistance indices (PVRIs). Hematological evaluation of the 10 patients showed marked anemia, markedly increased numbers of nucleated red blood cells (nRBCs), and serum ferritin. Mean platelet count, plasma beta2 thromboglobulin, and thrombin-antithrombin III complex levels were significantly increased. It was concluded that PHT can be found in splenectomized beta-Thal patients. Features associated with PHT were female sex, hemoglobin E/beta-Thal, status many years postsplenectomy, marked anemia, markedly increased nRBC count, thrombocytosis, and very high serum ferritin levels. PHT was not due to pulmonary emboli. Our findings suggested that severe PHT was due to increased PVRI from thrombotic pulmonary arteriopathy, likely from chronic low-grade hypercoagulability and platelet activation after splenectomy.
International Journal of Hematology 08/2003; 78(2):139-45. · 1.27 Impact Factor
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ABSTRACT: Patients with hemoglobin E/beta-thalassemia (E/beta-Thal) who have undergone splenectomy are prone to thrombosis in the small pulmonary arteries. To study the role of platelets in this situation, we assayed plasma beta2-thromboglobulin (betaTG) and performed whole blood platelet aggregation analysis of 30 E/beta-Thal patients, half of whom had undergone splenectomy. We compared results with those obtained with 15 healthy control subjects. Plasma betaTG levels in splenectomy patients were significantly higher than in control subjects and patients who had not undergone splenectomy, and platelets in splenectomy patients exhibited hyperaggregation in response to adenosine diphosphate, thrombin, and ristocetin. Levels of plasma thrombin-antithrombin III complex were also significantly higher. This finding is likely due to an increased number of erythrocytes with exposed phosphatidylserines, an effect that has been associated with splenectomy. The increased presence of thrombin in the blood may well be the cause of platelet hyperactivity, which was evident only in the asplenic patients Platelet hyperactivity very likely plays a pathogenetic role in the thrombosis of small pulmonary arteries that occurs in E/beta-Thal patients who have undergone splenectomy.
International Journal of Hematology 05/2003; 77(3):299-303. · 1.27 Impact Factor
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ABSTRACT: Small pulmonary arterial thromboses can occur following splenectomy of patients with haemoglobin E/beta-thalassaemia (Hb E/beta-thal). We compared plasma markers of coagulation activation in vivo and red blood cell (RBC) markers of procoagulant activity in 15 Hb E/beta-thal patients who were not splenectomized (NS), 15 who had been splenectomized (S), and 15 normal controls (NC). Levels of plasma thrombin-antithrombin III complex (TAT) were significantly higher in the S group than in either the NS or the NC groups, and levels of prothrombin fragment 1.2 (F 1.2) were significantly higher in the S than in the NC group. Diluted Russell's viper venom clotting times were significantly shorter when RBCs from group S patients were added to the assay compared with RBCs from the NC group. Phosphatidylserine (PS) expression (% of annexin V-positive RBCs) on the outer leaflet of RBC membrane of both 'larger'- and 'smaller'-sized RBCs was significantly higher for the S than the NC group. The RBC PS expression of the S and the NS groups, respectively, accounted for 25 x 3% (P = 0 x 174) and 6.3% (P = 0 x 675) of the variation in plasma TAT levels. Our findings indicated that, when compared with NC, splenectomized patients with Hb E/beta-thal were in a chronic low-grade hypercoagulable state associated with increased numbers of circulating PS exposed RBCs. This condition may have a role in the risk of these patients for pulmonary arterial thromboses.
British Journal of Haematology 10/2002; 118(3):893-8. · 4.94 Impact Factor
