Baseline factor VIII plasma levels and age at first bleeding in patients with severe forms of von Willebrand disease.

INTRODUCTION: von Willebrand disease (VWD) is the most common inherited bleeding disorder. The age of bleeding onset is highly variable, also in patients with similar degree of severity. AIM: The primary aim of this study was to evaluate whether baseline factor VIII (FVIII) plasma levels correlate with age at first bleeding in patients with extremely low levels of VWF:RCo (<6 IU dL(-1) ). METHODS: One hundred and three patients with VWF:RCo <6 IU dL(-1) (6 VWD1, 73 VWD2 and 24 VWD3) undergoing a medical examination between September 2010 and September 2013 were included. The relationship between baseline FVIII levels and age at first bleeding was tested in a multivariable linear regression model, adjusting for sex. RESULTS: The median age at first bleeding was lower in patients with VWD3 than in those with severe forms of VWD1 or VWD2 (1 year vs. 7 and 8 years, respectively, P < 0.0001). A positive non-linear relationship between FVIII levels and age at first bleeding was found, the latter increasing by 5 years for every 10 IU dL(-1) increase of FVIII (ß = 4.95 [95% CI: 2.02-7.87]) until levels of 30 IU dL(-1) , after which the age increased slowly. This relationship was not found in VWD 2A and 2B. In 65 patients (63%) there was a more than 6-month delay between bleeding onset and VWD diagnosis, with no difference over decades. CONCLUSIONS: Baseline FVIII plasma levels influence the age at bleeding onset in VWD patients with extremely low levels of VWF:RCo, except in those with types 2A and 2B.

Effect of prothrombin 19911 A>G polymorphism on the risk of cerebral sinus-venous thrombosis.

BACKGROUND AND PURPOSE: The A>G polymorphism at position 19911 of the prothrombin gene is associated with a mildly increased risk of venous thromboembolism, alone or in association with such common thrombophilia mutations as factor V Leiden and prothrombin 20210 GA. Its role in cerebral sinus-venous thrombosis (CSVT) is not known. METHODS: The presence of prothrombin 19911 A>G was investigated in a case­control study of 107 patients with cerebral thrombosis and factor V Leiden (n = 25), prothrombin 20210 GA (n = 47), without known thrombophilia (n = 35) and 842 healthy individuals with the corresponding coagulation profile. RESULTS: Prothrombin 19911 A>G did not increase the risk of CSVT in carriers of factor V Leiden (adjusted odds ratio 1.6, 95%CI 0.6­4.7), prothrombin 20210 GA (odds ratio 1.1, 95%CI 0.6­2.2), nor in patients without known thrombophilia (odds ratio 1.3, 95%CI 0.5­3.1). CONCLUSIONS: Prothrombin 19911 A>G polymorphism does not appear to be a risk factor for CSVT, alone or in association with factor V Leiden or prothrombin 20210GA.

The hemostatic system through aging and menopause.

The process of aging is accompanied by several modifications in the hemostatic system at different levels (blood coagulation, fibrinolysis, platelet activity, vascular endothelium). These changes may explain the higher incidence of arterial and venous thrombosis in the elderly compared to young people. Genetic and environmental factors modulate in different combinations the expression of proteins involved in the hemostatic process. Among the latter, diet and smoking habits play an important role, as well as physical exercise and, for women, hormonal status. A gradual and progressive development of a low-grade inflammatory state (clearly demonstrated in the elderly) is also an important factor that influences hemostasis during aging. In spite of the fact that the increased hypercoagulable state observed with aging may account for the higher incidence of thrombosis in the elderly, the finding of a similar pattern of coagulation activation in healthy centenarians suggests that a hypercoagulable state is compatible with health and longevity. Taking also into consideration that no laboratory parameters of hemostasis are predictive of thrombosis on an individual basis, a physician's behavior towards aging patients (e.g. prescription of hormonal replacement therapy to a woman during menopause) should not be affected by laboratory tests, but mainly by a patient's clinical history and the presence of strong risk factors for thrombosis other than age (e.g. diabetes mellitus, arterial hypertension, dyslipidemia, obesity, smoking).

The effect of recanalization on long-term neurological outcome after cerebral venous thrombosis.

Essentials The role of cerebral venous thrombosis (CVT) recanalization on neurologic outcome is still debated. We studied a large cohort of 508 CVT patients with 419 patient years of radiological follow-up. Recanalization rate is high during the first months after CVT and neurologic outcome is favorable. High recanalization grade of CVT independently predicts good neurological outcome. SUMMARY: Background Studies with limited sample size and with discordant results described the recanalization time-course of cerebral venous thrombosis (CVT). The neurological outcome after a first episode of CVT is good, but the role of recanalization on neurological dependence is still debated. Objectives The aim of the study is to assess the recanalization rate after cerebral venous thrombosis (CVT) and its prognostic role in long-term neurological outcome. Patients/Methods In a retrospective observational multicenter cohort study, patients with an acute first episode of CVT with at least one available imaging test during follow-up were enrolled. Patency status of the vessels was categorized as complete, partial or not recanalized. Neurological outcome was defined using the modified Rankin scale (mRS) as good (mRS = 0-1) or poor (mRS = 2-6). Results Five-hundred and eight patients (median [IQR] age, 39 [28.5-49] years; 26% male) were included. Complete or partial recanalization was not differently represented in patients undergoing scans at different periods of time (from 28-day to 3 month-period up to a 1-3 year-period). mRS at the time of follow-up imaging was available in 483 patients; 92.8% of them had a mRS of 0-1. CVT recanalization (odds ratio [OR], 2.56; 95% confidence interval [CI], 1.59-4.13) was positively associated, whereas cancer (OR, 0.29; 95% CI, 0.09-0.88), and personal history of venous thromboembolism (VTE) (OR, 0.36; 95% CI, 0.14-0.92) were negatively associated as independent predictors of favorable (mRS = 0-1) outcome at follow-up. Conclusions Most patients with a first CVT had complete or partial recanalization at follow-up. Recanalization was independently associated with a favorable neurological outcome.

Targeted sequencing to identify novel genetic risk factors for deep vein thrombosis: a study of 734 genes.

Essentials Deep vein thrombosis (DVT) has a large unknown genetic component. We sequenced coding areas of 734 hemostasis-related genes in 899 DVT patients and 599 controls. Variants in F5, FGA-FGG, CYP4V2-KLKB1-F11, and ABO were associated with DVT risk. Associations in KLKB1 and F5 suggest a more complex genetic architecture than previously thought. SUMMARY: Background Although several genetic risk factors for deep vein thrombosis (DVT) are known, almost all related to hemostasis, a large genetic component remains unexplained. Objectives To identify novel genetic determinants by using targeted DNA sequencing. Patients/Methods We included 899 DVT patients and 599 controls from three case-control studies (DVT-Milan, Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis [MEGA], and the Thrombophilia, Hypercoagulability and Environmental Risks in Venous Thromboembolism [THE-VTE] study) for sequencing of the coding regions of 734 genes involved in hemostasis or related pathways. We performed single-variant association tests for common variants (minor allele frequency [MAF] ≥ 1%) and gene-based tests for rare variants (MAF ≤ 1%), accounting for multiple testing by use of the false discovery rate (FDR). Results Sixty-two of 3617 common variants were associated with DVT risk (FDR < 0.10). Most of these mapped to F5,ABO,FGA-FGG, and CYP4V2-KLKB1-F11. The lead variant at F5 was rs6672595 (odds ratio [OR] 1.58, 95% confidence interval [CI] 1.29-1.92), in moderate linkage with the known variant rs4524. Reciprocal conditional analyses suggested that intronic variation might drive this association. We also observed a secondary association at the F11 region: missense KLKB1 variant rs3733402 remained associated conditional on known variants rs2039614 and rs2289252 (OR 1.36, 95% CI 1.10-1.69). Two novel variant associations were observed, in CBS and MASP1, but these were not replicated in the meta-analysis data from the International Network against Thrombosis (INVENT) consortium. There was no support for a burden of rare variants contributing to DVT risk (FDR > 0.2). Conclusions We confirmed associations between DVT and common variants in F5,ABO,FGA-FGG, and CYP4V2-KLKB1-F11, and observed secondary signals in F5 and CYP4V2-KLKB1-F11 that warrant replication and fine-mapping in larger studies.

Hemostatic abnormalities in patients with Ehlers-Danlos syndrome.

Essentials Ehlers-Danlos Syndrome (EDS) is a rare heterogeneous group of inherited collagen disorders. A cohort of EDS patients was investigated for bleeding tendency and hemostatic abnormalities. EDS is associated with an increased risk of bleeding. EDS patients have platelet function abnormalities, whose severity correlates with bleeding risk. SUMMARY: Background Ehlers-Danlos syndrome (EDS) includes a heterogeneous group of connective tissue disorders affecting skin, bones, vessels, and other organs. Patients with EDS have an increased risk of bleeding, but a comprehensive study of hemostasis in EDS patients is lacking. Objective To investigate the bleeding tendency of a cohort of patients with EDS by using the Bleeding Assessment Tool of the ISTH, the bleeding severity score (BSS). Methods The BSS was defined as abnormal when it was ≥ 4 in men and ≥ 6 in women. Patients with a bleeding tendency were compared with those without in terms of type and number of hemostatic abnormalities. Results Fifty-nine of 141 patients with EDS (41.7%) had an abnormal BSS. Prothrombin time and activated partial thromboplastin time were slightly prolonged in 10 patients (7.1%) because of mild coagulation factor deficiencies, which were not responsible for the bleeding diathesis. von Willebrand factor antigen, ristocetin cofactor, endogenous thrombin potential and platelet count were normal in all patients. At least one platelet function abnormality was found in 53 patients (90%) with an abnormal BSS and in 64 (78%) with a normal BSS (adjusted odds ratio [OR] 2.55, 95% confidence interval [CI] 0.87-7.48). The risk of bleeding progressively increased with the number of platelet function abnormalities, reaching an OR of 5.19 (95% CI 1.32-20.45) when more than three abnormalities were detected. Conclusions Our results show that nearly half of patients with EDS have an abnormal BSS, which, in 90% of cases, appear, at least in part, to be attributable to platelet function abnormalities. Abnormalities of primary hemostasis may contribute to the risk of bleeding in patients with EDS.

Usefulness of PFA-100 testing in the diagnostic screening of patients with suspected abnormalities of hemostasis: comparison with the bleeding time.

BACKGROUND: Global tests of hemostasis that are used to screen patients with clinical suspicion of bleeding disorders should help the physician to identify the phase of the hemostatic system that is abnormal and guide further diagnostic workup. PATIENTS AND METHODS: We compared the performance of Platelet Function Analyzer-100 (PFA-100) closure time (CT) with bleeding time (BT), both of which are screening tests for primary hemostasis, in the diagnostic workup of 128 consecutive patients who were screened for bleeding disorders. The sensitivities of BT and PFA-100 CT for known defects of hemostasis were evaluated; in addition, we calculated their correlation with the levels of severity of the bleeding symptoms, which were recorded using a standardized questionnaire. RESULTS: The sensitivity of PFA-100 testing was 71% for von Willebrand disease (VWD) [with both collagen-adenosine diphosphate (C-ADP) and collagen-epinephrine (C-EPI) cartridges]; 58% (C-EPI) and 8% (C-ADP) for platelet function disorders (PFDs); and the sensitivity of BT was 29% (VWD) and 33% (PFD). C-EPI CT was also prolonged in about 20% of patients with abnormalities of coagulation or fibrinolysis. Only the C-EPI CT was significantly associated with the levels of severity of the patients' bleeding scores. CONCLUSIONS: BT and C-EPI are insufficiently sensitive to be recommended as hemostasis screening tests. The C-ADP cartridge, which is sensitive to VWD only, might prove useful in further diagnostic workup of defects of primary hemostasis. The association of C-EPI CT with the severity of bleeding symptoms as a useful predictor of risk of bleeding in clinical practise should be tested in properly designed studies.

Minimal factor XIII activity level to prevent major spontaneous bleeds.

Essentials A strong association between bleeding severity and FXIII activity level (FXIII:C) was shown. The range 5-30 IU dL-1 of FXIII:C was associated with a high variability of bleeding severity. The PROspective study confirmed the association between FXIII:C activity and bleeding severity. A FXIII: C of 15 IU dL-1 is a proposed target to start prophylaxis for prevention of major bleeding. SUMMARY: Background Congenital factor XIII (FXIII) deficiency is a rare bleeding disorder associated with significant bleeding manifestations. The European Network of Rare Bleeding Disorders (EN-RBD) study, performed from 2007 to 2010, showed a strong association between bleeding severity and FXIII activity in plasma of patients with FXIII deficiency. Among these patients, variable levels of FXIII activity, from undetectable to 30%, were associated with a wide range of bleeding severity. Objectives and patients The present cross-sectional study, in the frame of the PRO-RBDD project, a prospective cohort study, analyzed data of 64 patients with FXIII deficiency and different types of clinical and laboratory severity. Results The results of this analysis confirmed that FXIII coagulant activity in plasma is well associated with clinical severity of patients. In addition, 15 IU dL-1 of FXIII activity was identified to be the level under which the probability of spontaneous major bleeding sharply increases (from 50% for levels of 15 IU dL-1 to more than 90% for levels of 5 IU dL-1 or lower). Conclusion The PRO-RBDD study suggests a FXIII coagulant activity level of 15 IU dL-1 as a target to start prophylaxis in order to prevent major bleedings, such as central nervous system or gastrointestinal tract hemorrhages.

External validation of the DASH prediction rule: a retrospective cohort study.

Essentials Predicting recurrences may guide therapy after unprovoked venous thromboembolism (VTE). We evaluated the DASH score in 827 patients with unprovoked VTE to verify prediction accuracy. A DASH score ≤ 1 had a cumulative recurrence risk at 1 year of 3.6%, as predicted by the model. The DASH score performed better in younger (< 65 years old) subjects. SUMMARY: Background The DASH prediction model has been proposed as a guide to identify patients at low risk of recurrence of venous thromboembolism (VTE), but has never been validated in an independent cohort. Aims To validate the calibration and discrimination of the DASH prediction model, and to evaluate the DASH score in a predefined patient subgroup aged > 65 years. Methods Patients with a proximal unprovoked deep vein thrombosis (DVT) or pulmonary embolism (PE) who received a full course of vitamin K antagonist or direct oral anticoagulant (> 3 months) and had D-dimer measured after treatment withdrawal were eligible. The DASH score was computed on the basis of the D-dimer level after therapy withdrawal and personal characteristics at the time of the event. Recurrent VTE events were symptomatic proximal or distal DVT/PE, and were analyzed with a time-dependent analysis. Observed 12-month and 24-month recurrence rates were compared with recurrence rates predicted by the DASH model. Results We analyzed a total of 827 patients, of whom 100 (12.1%) had an objectively documented recurrence. As compared with the original DASH cohort, there was a greater proportion of subjects with a 'low-risk' (≤ 1) DASH score (66.3% versus 51.6%, P < 0.001). The slope of the observed versus expected cumulative incidence at 2 years was 0.71 (95% confidence interval 0.51-1.45). The c-statistic was lower for subjects aged > 65 years (0.54) than for younger subjects (0.72). Conclusions These results confirm the validity of DASH prediction model, particularly in young subjects. The recurrence risk in elderly patients (> 65 years) was, however, > 5% even in those with the lowest DASH scores.

Pregnancy outcome after a first episode of cerebral vein thrombosis.

Essentials Little is known about recurrences and pregnancy outcome after cerebral vein thrombosis (CVT). We studied a cohort of pregnant women with CVT. Women with CVT appear at increased risk of late obstetrical complications despite prophylaxis. Risks of recurrent thrombosis and bleeding in women on heparin prophylaxis while pregnant are low. SUMMARY: Background The risk of recurrent thrombosis and bleeding episodes in women with previous cerebral vein thrombosis (CVT) on antithrombotic prophylaxis with low-molecular-weight heparin (LMWH) during pregnancy is not established and little information is available on pregnancy outcome. Objectives The aims of this study were to evaluate the risk of obstetrical complications, recurrent venous thrombosis and bleeding in a cohort of pregnant women on LMWH after a first episode of CVT. In addition, to estimate the relative risk of obstetrical complications, patients were compared with healthy women without thrombosis and with at least one pregnancy in their life. Patients We studied a cohort of 52 patients and 204 healthy women. Results The risk of developing late obstetrical complications was 24% (95% CI, 18-38%), leading to a relative risk of 6.09 (95% CI, 2.46-15.05). The risk of miscarriage was not increased. The higher risk of late obstetrical complications in patients appeared unrelated to a previous history of obstetrical complications, to the carriership of thrombophilia abnormalities, or to the presence of co-morbidities. The incidence of termination observed in patients with thrombophilia was double that observed in those without. No recurrent thrombosis or bleeding episodes were observed. Conclusions Women with previous CVT on LMWH prophylaxis during pregnancy have a low risk of developing recurrent thrombosis or bleeding episodes, but seem to have an increased risk of late obstetrical complications.

Low plasma levels of vitamin B(6) are independently associated with a heightened risk of deep-vein thrombosis.

BACKGROUND: Elevated plasma levels of total homocysteine (tHcy) before and after an oral methionine load (PML) are associated with an elevated risk of deep-vein thrombosis (DVT). We investigated whether plasma levels of B vitamins that are involved in Hcy metabolism are associated with an elevated risk of DVT. METHODS AND RESULTS: We compared 397 cases with previous DVT with 585 matched healthy controls. The plasma levels of folate, vitamin B(12), vitamin B(6,), and fasting and PML tHcy were measured. The ORs for DVT associated with high (>95th percentile) fasting levels and PML increases of tHcy were 2.1 (95% CI, 1.2 to 3.4) and 2.4 (95% CI, 1.5 to 3.9) after adjustment for established risk factors for DVT. Fasting plasma levels and PML increases in tHcy correlated negatively with vitamin levels. The crude OR for folate levels in the lowest quartile compared with the highest was 1.5 (95% CI, 1.1 to 2.1), and that for B(6) levels in the lowest and second quartiles compared with the highest was 1.5 (95% CI, 1.0 to 2.1). However, after adjustment for established risk factors and fasting and PML tHcy, the ORs for B(6) levels in the lowest and second quartiles only remained statistically significant (lowest quartile: OR, 1.8; 95% CI, 1.2 to 2.8; second quartile, OR, 1.9; 95% CI, 1.3 to 2.9). CONCLUSIONS: High fasting and PML tHcy and low vitamin B(6) plasma levels are associated with an elevated risk for DVT independently of established risk factors for DVT. The association of low vitamin B(6) levels with the risk for DVT is independent of fasting and PML tHcy levels.

Patients with type 3 severe von Willebrand disease are not protected against atherosclerosis: results from a multicenter study in 47 patients.

BACKGROUND: The results of a number of studies in pigs and mice suggest that absence of von Willebrand factor (vWF) protects against the development of atherosclerosis. We studied whether patients with a complete deficiency of vWF (type 3 von Willebrand disease [vWD]) develop fewer atherosclerotic vessel wall changes than healthy controls. METHODS AND RESULTS: This study included 47 individuals with type 3 vWD and 84 healthy controls. Early atherosclerotic changes were assessed by measuring the thickness of the intima-media in the carotid and femoral arteries by B-mode ultrasonography. Advanced atherosclerotic changes were quantified by summing the maximal thickness of atherosclerotic plaques in the carotid and femoral arteries and were expressed as a plaque score. Established risk factors were determined to adjust for possible differences between the groups. We found no substantial difference in intima-media thickness between vWD patients and controls (adjusted difference for carotid artery 0.007 mm, 95% CI -0.022 to 0.036 mm; femoral artery 0.069 mm, 95% CI -0.056 to 0.19 mm). Similar proportions of patients and controls had atherosclerotic plaques (19% and 17%, respectively). No difference was found in the plaque score between groups (adjusted difference -0.22 mm, 95% CI -0.69 to 0.26). Among vWD patients, we found no effect of treatment with vWF concentrates on intima-media thickness or plaque score. CONCLUSIONS: The results of this study indicate that vWF does not play a substantial role in human atherogenesis.

Evaluation of an heterogeneous group of patients with von Willebrand disease using an assay alternative to ristocetin induced platelet agglutination.

BACKGROUND: Diagnosis of von Willebrand disease (VWD) type 2 usually relies on the discrepancy between the von Willebrand factor (VWF) ristocetin cofactor activity (VWF:RCo) and VWF antigen (VWF:Ag). Type 2B patients can be discriminated from other qualitative VWD variants by using ristocetin-induced platelet agglutination (RIPA) test. The major limitation of RIPA is the requirement of fresh blood sample. OBJECTIVES: In this study, we evaluated the VWF gain-of-function mutant GPIb binding (VWF:GPIbM) and VWF:RCo assays to investigate whether the VWF:GPIbM/VWF:RCo ratio was able to identify the type 2B variant among an heterogeneous VWD population, previously characterized following the ISTH-SSC guidelines. PATIENTS/METHODS: Seventy-six VWD patients and 31 healthy subjects were evaluated by using VWF:Ag, VWF:RCo, and VWF:GPIbM assays. RESULTS: The mean (minimum-maximum values) VWF:GPIbM/VWF:RCo ratio was higher in type 2B patients (2.53, 0.84-6.11) than in healthy controls (1.05, 0.87-1.34), type 1 (0.85, 0.51-1.15), 2A (1.20, 0.36-2.82), and 2M (1.07, 0.91-1.38) (P < 0.0001). Type 2B variants were divided into four groups (A, B, C, and D) according to their different multimeric patterns. The mean value of the VWF:GPIbM/VWF:RCo ratio in the four groups showed an increasing trend from group A (1.08) to D (3.69), proportional to the loss of high molecular weight multimers. Among 32 type 2B patients, previously diagnosed with RIPA, 8 (mainly with a type I New York/Malmö phenotype) were not confirmed using the VWF:GPIbM/VWF:RCo ratio. CONCLUSIONS: Whenever the RIPA test is not feasible, the VWF:GPIbM/VWF:RCo ratio might help to identify severe type 2B VWD patients.

Predictors of von Willebrand disease diagnosis in individuals with borderline von Willebrand factor plasma levels.

BACKGROUND: In individuals with borderline von Willebrand factor (VWF) plasma levels, second-level tests are required to confirm or exclude von Willebrand disease (VWD). These tests are time-consuming and expensive. OBJECTIVE: To assess which parameters can predict VWD diagnosis in individuals with borderline VWF levels (30-60 IU dL(-1) ). METHODS: Nine hundred and fifty individuals with bleeding episodes or abnormal coagulation test results were investigated with first-level tests (blood count, prothrombin time, activated partial thromboplastin time, blood clotting factor VIII, VWF ristocetin cofactor activity [VWF:RCo], and VWF antigen), and 93 (62 females and 31 males; median age, 28 years; interquartile range 15-44) had borderline VWF:RCo levels. All underwent second-level investigations to confirm or exclude VWD. A multivariable logistic regression model was fitted with sex, age, bleeding score, family history, VWF:RCo and ABO blood group as predictors, and used to predict VWD diagnosis. RESULTS: Forty-five of the 93 individuals (48%) had VWD (84% type 1). A negative linear relationship between VWF:RCo levels and risk of VWD diagnosis was present, and was particularly evident with blood group non-O [adjusted odds ratio 7.00 (95% confidence interval [CI] 1.48-33.11) for every 5 IU dL(-1) decrease in VWF:RCo]. The other variable clearly associated with VWD diagnosis was female sex (adjusted odds ratio 5.76 [95% CI 1.47-22.53]). The area under the receiver operating characteristic curve of the full logistic model was 0.89 (95% CI 0.82-0.95). CONCLUSIONS: In individuals with borderline VWF, the two strongest predictors of VWD diagnosis are low VWF:RCo levels (particularly in those with blood group non-O) and female sex. This predictive model has a promising discriminative ability to identify patients with borderline VWF levels who are likely to have VWD.

Arterial intima-media thickness and its relationship with cardiovascular disease and atherosclerosis: a possible contribution of medium-sized arteries.

The intima-media thickness (IMT) of the arterial wall, measured by B-mode ultrasonography, has been related to cardiovascular disease and atherosclerosis in many studies, most of which have considered carotid and common femoral arteries. No study has related the IMT of medium-sized arteries (e.g. brachial) to the atherosclerotic process. The aim of this study was to evaluate whether more peripheral arteries (e.g. brachial, superficial femoral and popliteal) represent a good model in studies of arterial wall IMT, as well as carotid artery. Twenty-six male patients with demonstrated coronary artery disease (median age 63 yrs; range 41-70) and twenty-four male controls (median age 62 yrs; range 53-74) were studied. The far-wall IMT of the common carotid, brachial, superficial femoral and popliteal arteries was measured by high-resolution B-mode ultrasonography. Its relationship with ischemic cardiovascular disease and the presence of atherosclerotic plaques in all the arteries was also evaluated. Mean IMT values were higher in patients than controls, more so in superficial femoral artery (IMT difference 0.08 mm [95% confidence interval 0.02 - 0.14]) and popliteal artery (0.08 [0.01-0.15]) than in common carotid artery (0.02 [-0.07-0.11]) or brachial artery (0.01[-0.01-0.03]). The difference did not change after adjustment for age. The prevalence of plaques was consistently higher in patients than controls, except for brachial artery, in which no plaque was found either in patients and controls. In all the arteries except brachial we found an association between increase in IMT and number of plaques. Age was strongly related to the presence of plaques in the carotid artery, and less markedly in superficial femoral and popliteal arteries. The brachial artery does not seem a good model to study atherosclerosis by ultrasound measurements of arterial IMT, whereas superficial femoral and popliteal arteries might be chosen for these studies besides carotid artery.

Evaluation of the PFA-100 system in the diagnosis and therapeutic monitoring of patients with von Willebrand disease.

We have evaluated platelet function at high shear with the PFA-100 system in different subtypes of von Willebrand disease (vWD), before and after the intravenous infusions of desmopressin or a factor-VIII/von Willebrand factor (vWF) concentrate. Closure times with the PFA-100 system were determined for both the collagen/ADP and the collagen/epinephrine cartridges in 52 patients with vWD (9 type 1 "platelet normal", 5 type 1 "platelet-discordant", 8 type 1 "platelet-low", 6 type 2A, 9 type 2B, 6 type 2M Vicenza. 6 type 3 and 3 acquired vWD) and 40 controls. Measurements were repeated 1 and 4 h after the i.v. infusion of desmopressin (0.3 microg/Kg) in 26 patients with types 1, type 2M Vicenza or type 2A vWD, or of a factorVIII/vWF concentrate (Alphanate HT, 60 U/Kg) in 4 patients with type 3 vWD. At all time points, vWF plasma levels and the bleeding time (Symplate II) were also determined. Baseline closure times were longer in vWD patients than in controls with both the collagen/ADP and the collagen/ epinephrine cartridges. The sensitivity of the PFA-100 system (88% and 87% with the two cartridges) was higher than that of the bleeding time (65%). Treatment with desmopressin normalized the closure times in patients with type 1 "platelet-normal" or type 2M Vicenza vWD, had no significant effects in patients with type 1 "platelet-low", type 1 "platelet-discordant" or type 2A vWD. Infusion of a factorVIII/vWF concentrate in patients with type 3 vWD slightly shortened their prolonged closure times. In general, changes in PFA-100 were paralleled by shortenings of the bleeding times and increases in plasma vWF levels. The PFA-100 test reflects vWF-dependent platelet function under high shear stress and could be useful in the diagnosis and therapeutic monitoring of patients with vWD.

Risk of pregnancy-related venous thrombosis in carriers of severe inherited thrombophilia.

Homozygous carriers of factor V Leiden have an approximately 80-fold increased risk of venous thrombosis. Also double heterozygous carriers of both the factor V Leiden and the prothrombin gene mutations are at high thrombotic risk. The magnitude of the risk of venous thrombosis in pregnant women with the two severe thrombophilic conditions has not been estimated so far. We performed a multicenter retrospective family study in women with homozygous factor V Leiden, double heterozygous factor V Leiden and the prothrombin gene mutation, and women with normal coagulation. Only relatives of index patients with thrombosis formed the study cohort. Fifteen homozygous and 39 double heterozygous women were compared to 182 women with normal coagulation. Venous thrombosis occurred in 3 of 19, 2 of 50 and 1 of 221 pregnancies, respectively. One thrombotic episode occurred in the third trimester, the remaining 5 in the postpartum. The prevalence of venous thrombosis was 15.8% (95% CI 3.4-39.6) for homozygotes. 4.0% (95% CI 0.5-13.7) for double heterozygotes and 0.5% for women with normal coagulation. The relative risk of pregnancy-related venous thrombosis was 41.3 (95% CI 4.1-419.7) for homozygous and 9.2 (95% CI 0.8-103.2) for double heterozygous carriers. In conclusion, homozygous carriers of factor V Leiden and, to a lesser extent, double heterozygous carriers of factor V Leiden and of the prothrombin mutation have an increased risk of venous thrombosis during pregnancy, particularly high during the postpartum period. On the basis of these findings we recommend that these women receive anticoagulant prophylaxis at least in the postpartum, that should perhaps be extended to the whole pregnancy in homozygous carriers.

Acquired von Willebrand syndrome: data from an international registry.

The acquired von Willebrand syndrome (AvWS) is a rare bleeding disorder with laboratory findings similar to those of congenital von Willebrand disease (vWD). Despite the numerous cases reported in the literature until 1999 (n = 266), large studies on AvWS are not available. Moreover, diagnosis of AvWS has been difficult and treatment empirical. These considerations prompted us to organize an international registry. A questionnaire, devised to collect specific information on AvWS, was sent to all the members of the International Society on Thrombosis and Haemostasis (ISTH), who were invited to respond if they had diagnosed cases with the AvWS cases. 156 members answered the questionnaire and 54 of them sent information on 211 AvWS cases from 50 centers. Data were compared with those already published in the literature and 25 cases already described or not correctly diagnosed were excluded. The 186 AvWS cases that qualified for the registry were associated with lymphoproliferative (48%) and myeloproliferative disorders (15%), neoplasia (5%), immunological (2%), cardiovascular (21%) and miscellaneous disorders (9%). Ristocetin cofactor activity (vWF:RCo) or collagen binding activity (vWF:CBA) were usually low in AvWS (median values 20 U/dL, range 3-150), while factor VIII coagulant activity was sometimes normal (median 25 U/dL, range 3-191). FVIII/vWF inhibiting activities were present in only a minority of cases (16%). Bleeding episodes in AvWS were mostly of mucocutaneous type (68%) and were managed by DDAVP (32%), FVIII/vWF concentrates (37%), intravenous immunoglobulins (33%), plasmapheresis (19%), corticosteroids (19%) and immunosuppressive or chemotherapic agents (35%). Based upon the data of this international registry, it appears that AvWS is especially frequent in lympho- or myeloproliferative and cardiovascular diseases. Therefore, AvWS should be suspected and searched with the appropriate laboratory tests especially when excessive bleeding occurs in patients with these disorders. On the basis of the information provided by this registry guidelines for diagnosis and management of the AvWS are given.

A simplified procedure for thromboplastin calibration--the usefulness of lyophilized plasmas assessed in a collaborative study.

The International Sensitivity Index (ISI) of thromboplastins is determined by calibration using fresh plasmas from 60 patients stabilized on oral anticoagulants and 20 healthy subjects. This procedure is demanding, particularly for those who have no easy access to patients. The alternative use of a smaller number of lyophilized plasmas has already been considered, but one important issue, the number of repeated measurements to be carried out, has never been addressed. Two commercial rabbit thromboplastins, A and B, were calibrated in 3 laboratories against CRM 149R. On each of 10 working days, prothrombin times were measured for a different set of 8 fresh plasmas and for the same set of 8 lyophilized plasmas. The ISI values for both thromboplastins were estimated by orthogonal regression on fresh and lyophilized plasmas. The between- and within-laboratory CV values of the estimated ISI were taken as measures of precision of the calibration. In addition, ISI and CV were calculated daily on cumulative results obtained with lyophilized plasmas from day 1 to day 10. The ISI values for both thromboplastins calculated with lyophilized plasmas were not significantly different from those with fresh plasmas (mean of 3 laboratories: 1.42 vs 1.48 for A and 1.22 vs 1.20 for B). The between-laboratory precision of the calibration with lyophilized plasmas was not considerably different from that with fresh plasmas (CV for 3 labs: 5.2% vs 6.8% for A and 0.9% vs 2.2% for B). The ISI estimated with lyophilized plasmas on results of day 1 were not different from those of days 2 through 10. Good within-laboratory precision of the calibration (CV around 2%) was already achieved on day 3. In conclusion, this study shows that lyophilized plasmas pooled from normals and patients on oral anticoagulants can be used as substitutes for individual fresh plasmas to simplify the existing procedure for thromboplastin calibration.