Gregor Hron

Tissue factor-positive microparticles : Cellular origin and association with coagulation activation in patients with colorectal cancer

The pathogenesis of hypercoagulability in cancer is not entirely understood. We hypothesized that in cancer patients circulating tissue factor-positive microparticles (TF (+) MPs) are increased and associated with hemostatic system activation. In 20 patients with advanced colorectal cancer and in 20 age- and sex-matched controls, number and cellular origin of TF (+) MPs were determined in plasma by flow cytometry. D-dimer was determined as an indicator of hemostatic system activation. Compared to controls, the median (interquartile range) number of TF (+) MPs was two-fold higher in cancer patients: 25.9 (15.4 - 42.0) x 10 (3) /ml plasma versus 13.1 (11.9 - 19.7) x 10 (3) /ml plasma, p = 0.007. This was mainly due to a higher amount of TF (+) MPs from platelets (13.4 [5.0 - 17.4] x 10 (3) /ml plasma vs. 5.8 [4.5 - 7.5] x 10 (3) /ml plasma, p = 0.017). TF (+) MPs correlated with D-dimer ( ? = 0.48, p = 0.002). High levels of TF (+) MPs in cancer patients and their correlation with D-dimer suggest that TF (+) MPs might be involved in hemostasis activation in cancer patients.

Overweight, Obesity, and the Risk of Recurrent Venous Thromboembolism

BACKGROUND Excess body weight is a risk factor for a first venous thromboembolism. The impact of excess body weight on risk of recurrent venous thrombosis is uncertain. METHODS We studied 1107 patients for an average of 46 months after a first unprovoked venous thromboembolism and withdrawal of anticoagulant therapy. Excluded were pregnant patients, those requiring long-term antithrombotic treatment, and those who had a previous or secondary thrombosis, natural coagulation inhibitor deficiency, lupus anticoagulant, or cancer. Our study end point was symptomatic recurrent venous thromboembolism. RESULTS A total of 168 patients had recurrent venous thromboembolism. Mean (SD) body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) was significantly higher among patients with recurrence than among those without recurrence: 28.5 (6.0) vs 26.9 (5.0) (P = .01). The relationship between excess body weight and recurrence was linear; the adjusted hazard ratio for each 1-point increase in BMI was 1.044 (95% confidence interval [CI], 1.013-1.076) (P < .001). Four years after discontinuation of anticoagulant therapy, the probability of recurrence was 9.3% (95% CI, 6.0%-12.7%) among patients of normal weight and 16.7% (95% CI, 11.0%-22.3%) and 17.5% (95% CI, 13.0%-22.0%) among overweight and obese patients, respectively. Compared with patients of normal weight, the hazard ratio of recurrence adjusted for age, sex, factor V Leiden, prothrombin G20210A mutation, high factor VIII levels, and type of initial venous thromboembolic event was 1.3 (95% CI, 0.9-1.9) (P = .20) among overweight patients and 1.6 (95% CI, 1.1-2.4) (P = .02) among obese individuals. The population attributable risk corresponding to excess body weight was 26.8% (95% CI, 5.3%-48.2%). CONCLUSION Excess body weight is a risk factor of recurrent venous thromboembolism.

Prediction of Recurrent Venous Thromboembolism by Endogenous Thrombin Potential and D-Dimer

BACKGROUND Increased thrombin generation is associated with an increased risk of recurrent venous thromboembolism. We investigated the relation between endogenous thrombin potential (ETP) and risk of recurrent venous thromboembolism and evaluated whether prediction of recurrence can be improved by a combined analysis of ETP and D-dimer. METHODS We followed 861 patients with first spontaneous venous thromboembolism and determined ETP and D-dimer after discontinuation of anticoagulation. Patients with natural inhibitor deficiency, lupus anticoagulant, or cancer were excluded. The study endpoint was symptomatic recurrent venous thromboembolism. RESULTS One hundred thirty patients (15.1%) had recurrence. High ETP (> or = 100%) conferred a 1.6-fold increased risk of recurrence (95% CI 1.1-2.3) after adjustment for age, sex, factor V Leiden, factor II G20210A, and duration of anticoagulation. After adjustment for D-dimer, risk of recurrence remained significantly higher among patients with high ETP [hazard ratio 1.6 (95% CI 1.01-2.4)]. After adjustment for ETP, high D-dimer (> or = 0.5 mg/L) conferred a 1.8-fold (95% CI 1.1-2.8) increased risk of recurrence. Compared with patients with low ETP and low D-dimer, risk of recurrence was 2.8-fold (95% CI 1.5-5.3) higher among patients with both high ETP and high D-dimer after adjustment for potential confounders. CONCLUSIONS ETP and D-dimer are independent predictors of recurrent venous thromboembolism. Assessing risk of recurrence can be optimized by combining these indicators of thrombin generation.

Circulating P-selectin and the risk of recurrent venous thromboembolism

The clinical relevance of high P-selectin levels in venous thrombosis is unknown. We prospectively followed 544 patients with first unprovoked venous thromboembolism (VTE) after cessation of anticoagulation and evaluated P-selectin as a risk factor of recurrent VTE. VTE recurred in 63 (12%) patients. Patients with recurrence had significantly higher P-selectin levels than those without (45.8 mg/dl +/- 16.4 vs. 40.1 mg/dl +/- 13.3; p = 0.006). After four years, the probability of recurrence was 20.6% (95% confidence interval [CI] 12.6-28.5) among patients with P-selectin values above the 75(th) percentile of the patient population and was 10.8% (95% CI 7.2-14.3) among patients with lower values (p = 0.046). Compared to patients with low P-selectin, adjusted risk of recurrence was 1.7-fold (95% CI 1.0-2.9, p = 0.045) increased among patients with P-selectin levels exceeding the 75(th) percentile. We conclude that high circulating P-selectin is a risk factor of recurrent VTE.

Low dose acetylsalicylic acid and shedding of microparticles in vivo in humans.

Eur J Clin Invest 2010; 40 (6): 477–482

Marburg I polymorphism of factor VII-activating protease and risk of recurrent venous thromboembolism

Whether a single nucleotide polymorphism (1601 G > A) in the factor VII-activating protease gene (FSAP Marburg I) is a risk factor for venous thromboembolism (VTE) is unclear. We investigated the relevance of the variant with respect to recurrentVTE. 854 patients with a first unprovoked VTE were followed for an average of 41 months after discontinuation of anticoagulation. Study endpoint was symptomatic recurrent VTE. VTE recurred in 7 of 41 patients (17%) with and in 106 of 813 patients (13%) without the variant. After 3 years, the probability of recurrence was 20.0% (95% CI, 5.3% to 34.6%) among patients with and 12.2% (95% CI, 9.6% to 14.8%) among those without FSAP Marburg I (p = 0.5). The relative recurrence risk among carriers of the variant was 1.3 (95% CI, 0.6 to 2.8; p = 0.5) before and 1.5 (95% CI, 0.7 to 3.3; p = 0.3) after adjustment for potentially confounding factors. We conclude that FSAP Marburg I is, if at all, only a mild factor for recurrent VTE. Patients with FSAP Marburg I most probably will not benefit from extended anticoagulation.

Tissue factor exposing microparticles in inflammatory bowel disease

BACKGROUND Circulating procoagulant microparticles (MPs) are thought to be involved in the pathogenesis of venous thromboembolism in patients with inflammatory bowel disease (IBD). However, the exposure of tissue factor, the primary initiator of coagulation activation, on microparticles (TF(+)MPs) and its association with hemostasis activation has not yet been studied in IBD patients. METHODS In this case-control study 49 IBD patients (28 Crohns disease, 21 ulcerative colitis) and 49 sex- and age-matched, healthy controls were included. Clinical disease activity (Crohns Disease Activity Index and Clinical Activity Index, respectively) was assessed and IBD-related data were determined by chart review. Numbers, cellular origin and procoagulant activity of TF(+)MPs in plasma were determined using flow cytometry and a chromogenic activity assay. D-dimer and high-sensitive C-reactive protein (CRP) served as markers for coagulation activation and inflammation, respectively. The primary endpoint was the number of TF(+)MPs in IBD patients compared to controls. RESULTS Median number (interquartile range) of TF(+)MPs was higher in IBD patients than in controls (14.0 (11.9-22.8)×10(3)/mL vs. 11.9 (11.9-19.1)×10(3)/mL plasma, P=0.029). This finding was due to generally higher plasma levels of MPs from platelets and leukocytes in IBD patients. However, the number of TF(+)MPs was neither correlated with their procoagulant activity and D-dimer nor with disease activity and CRP. CONCLUSIONS Increased numbers of circulating TF(+)MPs represent a new facet of hemostatic abnormalities in IBD. However, the lack of association with activation of the coagulation system and disease activity questions their pathogenetic role for venous thromboembolism in this patient group.

Prediction of recurrent venous thromboembolism by measuring ProC Global.

In patients with venous thromboembolism (VTE) a laboratory assay that globally measures the overall thrombophilic tendency is not available. We hypothesized that determination of ProC((R)) Global, a plasma assay which tests the global function of the protein C pathway, could be used to stratify patients according to their risk of recurrent VTE. We prospectively followed 774 patients with first spontaneousVTE for a mean time of 52 months. ProC Global normalized ratio (NR) was measured in plasma by use of a commercially available assay based on activated partial thromboplastin time. Ninety-eight of the 774 patients had recurrentVTE. Patients with ProC Global NR > or = 0.75 had a relative risk of recurrence of 0.59 (95% CI 0.40-0.87) as compared with those with lower ratio. After four years, cumulative probability of recurrence was 8.6% in patients with ProC Global NR > or = 0.75 and 17.4% in patients with a lower ratio (p = 0.006). Patients with a high ProC Global NR have a low risk of recurrent VTE. ProC Global NR can be used to stratify patients with a first unprovoked VTE according to their risk of recurrence.

ProCGlobal and endogenous thrombin potential during pregnancy

OBJECTIVE Pregnancy is a hypercoagulable state. We evaluated global markers of coagulation activation, ProCGlobal (Siemens Healthcare Diagnostics, Eschborn, Germany) and endogenous thrombin potential (ETP), in pregnant women with and without low-molecular-weight (LMW) heparin prophylaxis. STUDY DESIGN We prospectively followed 113 healthy women and 61 women receiving LMW heparin prophylaxis throughout pregnancy. ProCGlobal and ETP were measured in venous blood during the first, second, and third trimester. RESULTS ProCGlobal decreased significantly throughout pregnancy in all women and was lower in anticoagulated women (P < .001 for all comparisons). ETP levels remained unchanged until the third trimester and then significantly decreased in all women. ETP was higher in anticoagulated women than in healthy women at all time points. CONCLUSION ProCGlobal levels decrease throughout pregnancy. In pregnant women at high thrombotic risk, coagulation activation reflected by low ProCGlobal and high ETP levels is substantial despite LMW heparin prophylaxis.