Absence of Missense Variant Detection in Inherited Dysfibrinogenemia May Result from a Poor Raw Data Analysis Algorithm or Mosaicism.

Variant identification underlying inherited dysfibrinogenemia quite exceptionally fails. We report on two dysfibrinogenemia cases whose underlying DNA variant could not be identified by Sanger analysis. These failures result from two distinct mechanisms. The first case involved raw signal overcorrection by a built-in software, and the second constituted the first description of mosaicism for one of the fibrinogen genes. This mosaicism was subsequently identified by next-generation sequencing reanalysis of the sample.

Effect of rivaroxaban and dabigatran on platelet functions: in vitro study.

INTRODUCTION: Clinical benefit-risk balance of direct oral anticoagulants (DOAC) in atherothrombosis prevention differs between anti-Xa and anti-IIa drugs and their specific effect on platelet functions remains controversial. We hence investigated rivaroxaban and dabigatran effect on platelets in identical experimental conditions. MATERIALS AND METHODS: Blood of fifteen healthy volunteers was spiked with DOAC which plasma concentrations were measured by specific anti-Xa or anti-IIa assays. Light transmission aggregometry measured in platelet-rich plasma used low doses of agonists: 0.5 mM arachidonic acid, 2.5 µM ADP, 0.5 µM epinephrine, 0.8 µg/ml collagen, 7.5 µM TRAP-6 and 0.5 pM tissue factor in the presence of H-Gly-Pro-Arg-Pro-OH to prevent fibrin polymerization. Platelet adhesion on collagen fibres was evaluated in whole blood under flow. Same experiments were reproduced in the presence of aspirin. RESULTS: Median [95% CI] plasma concentrations were of 28 [23-36], 128 [119-144] and 321 [293-361] ng/ml for rivaroxaban and 39 [34-45], 171 [166-193] and 353 [349-382] ng/ml for dabigatran. DOAC did not modify platelet aggregation or adhesion on collagen fibres at any tested concentrations. However, they delayed platelet aggregation secondary to coagulation activation with a more potent effect with dabigatran (p < 0.001). Aspirin did not modify DOAC effect. CONCLUSION: Efficacy of combining DOAC and aspirin in atherothrombosis prevention would not stem from a direct antiplatelet effect of the formers but to their additive inhibitory effect on platelet aggregation secondary to coagulation activation. This effect differs according to DOAC molecules and may also result from the pleiotropic roles of the different coagulation factors targeted by DOAC.

Impact of a pneumatic tube system transport on hemostasis parameters measurement: the experiment of Cochin universitary hospital (AP-HP, Paris, France).

Samples transported by pneumatic tube system are submitted to forces of acceleration and deceleration which can affect laboratory parameters. At Cochin hospital, majority of samples of hemostasis, except for platelets tests, are transported by pneumatic tube system. The objective of this study was to evaluate the impact of a pneumatic tube system (PTS) transport compared to hand-delivered transport on samples and to qualify Cochin hospital PTS according to requirements of standard ISO 15189. A bibliographical study was made and showed that pneumatic tube system particularly influences platelets tests. Four citrate tubes were collected in 5 healthy volunteers in the maternity: 2 tubes were transported by PTS and 2 others were hand-delivered to the laboratory. Five coagulation tests were analyzed: prothrombine time (PT), activated partial thromboplastin time (aPTT), factor (F) V, FVIII and platelet closure time with PFA-100TM collagen/epinephrine. For each volunteer, the results obtained by PTS and by hand-delivered transport were compared with formula usually used for biological analysis retake: 2.8 x standard deviation of reproductibility variation coefficient (SH GTA 01, COFRAC). This study did not show an impact of PTS on PT, aPTT, FV and FVIII. For PFA-100TM collagen/epinephrine, we noted an impact on 2/5 volunteers. These results, in agreement with the literature, led to the conclusion that Cochin hospital PTS is in compliance to transport samples for usual coagulation tests except platelet tests. This study allowed to issue French recommendations for PTS transport of hemostasis tubes qualification available on "Groupe français d'hémostase et thrombose" Web site.

PT, aPTT, TT and the hemostatic safety threshold of dabigatran and rivaroxaban.

The proposals of the Working group on perioperative hemostasis (Groupe d'intérêt en hémostase péri-opératoire (GIHP)) concerning the perioperative management of patients receiving the direct oral anticoagulants (DOACs) are based on the measure of their anticoagulant activities (anti-Xa for rivaroxaban and anti-IIa for dabigatran) with a safety threshold ≤ 30 ng/mL. If the dosage of the drug is not available, proposals are based on the combination of a PT ≥80% and an aPTT ≤1.20. The aim of our study was to evaluate the performance of PT, aPTT and thrombin time to predict values above or below the safety threshold. The measurement of DOACs concentration was carried out in 64 samples from patients treated with rivaroxaban and 48 samples from patients treated with dabigatran. The PT and aPTT were measured for all samples, while the TT was measured only for patients receiving dabigatran. The absence of agreement between the global hemostasis tests and the DOACs concentrations was observed for 10% of patients receiving dabigatran and 27% of patients with rivaroxaban treatment. Apart from dabigatran for which the predictive negative value of PT and aPTT or TT allows to exclude a concentration >30 ng/mL in 100% of cases, our results highlight the risk of misinterpretation when using global coagulation tests (PT and aPPT) for determination of the safety threshold for patients receiving the DOACs.

Peri-procedural management of dabigatran and rivaroxaban: Duration of anticoagulant discontinuation and drug concentrations.

BACKGROUND: Peri-procedural management of direct oral anticoagulants (DOAC) is challenging. The optimal duration of pre-procedural discontinuation that guarantees a minimal DOAC concentration ([DOAC]) at surgery is unknown. The usual 48-hour discontinuation might not be sufficient for all patients. OBJECTIVES: To test the hypothesis that a 48-hour DOAC discontinuation is not sufficient to ensure a minimal per-procedural [DOAC], defined as [DOAC]<30ng/mL. To investigate the factors associated with per-procedural [DOAC]. To evaluate the ability of normal PT and aPTT to predict [DOAC]<30ng/mL. METHODS: Patients treated with dabigatran or rivaroxaban, and requiring any invasive procedure were included in this multicentre, prospective, observational study. [DOAC], PT and aPTT were measured during invasive procedure. RESULTS: Sixty-five patients were enrolled. Duration of DOAC discontinuation ranged from 1-168h. Per-procedural [DOAC] ranged from <30 to 466ng/mL. [DOAC]<30ng/mL occurred more frequently after 48-hour discontinuation than after a shorter delay. [DOAC] remained ≥30ng/mL in 36% and 14% of measurements performed 24-48h and 48h-120h after discontinuation, respectively. According to ROC curve, a cut-off value of 120hours for DOAC discontinuation had a better specificity than a cut-off value of 48hours to predict [DOAC]<30ng/mL. Normal PT and aPTT ratios had good specificity and positive predictive value, but limited sensitivity (74%) and negative predictive value (73%) to predict [DOAC]<30ng/mL. CONCLUSIONS: A 48-hour discontinuation does not guarantee a [DOAC]<30ng/mL in all patients. Normal PT and aPTT are flawed to predict this threshold and could not replace specific assays. Further studies are needed to define the relationship between per-procedural [DOAC] and clinical outcomes.

Prevalence of Hereditary Thrombophilia in Patients Older Than 75 Years With Venous Thromboembolism Referred for Thrombophilia Screening.

BACKGROUND: Few studies focused on genetic risk factors for venous thromboembolism (VTE) in the very elderly people. In patients aged 75 years and older with VTE referred for laboratory screening tests for thrombophilia, we aimed: (i) to estimate the F5G1691A and F2G20210A mutation prevalence; (ii) to compare prevalence rates with those of a control group; and (iii) to compare the prevalence rates between patient subgroups, defined as with one or multiple VTE episodes and with provoked/unprovoked VTE. METHODS: Data were extracted from two prospective thrombophilia registries according to the following inclusion criteria: Caucasian patients aged 75 years and older presenting with at least one confirmed VTE episode. Associated VTE risk factors had been recorded using a standardized questionnaire. Laboratory tests included plasma antithrombin, protein C, and protein S activity measurements and F5G1691A and F2G20210A genotyping. RESULTS: Of the 312 patients (mean age: 84 ± 6 years; 245 women and 67 men), 47.1% had two or more VTE episodes and 63.5% patients had unprovoked VTE. None had deficiencies in antithrombin, protein C, or protein S. The F5G1691A and F2G20210A mutations were found in 29 (9.3%, 95% confidence interval [CI]: 6.3-13.1) and 18 (5.8%, 95% CI: 3.5-9.0) patients, respectively, versus 3.4% (95% CI: 1.9-4.9) and 3.1% (95% CI: 2.6-3.5) in control subjects (p = .0002 and p = .0082, respectively). Overall, 45 (14.4%) patients carried at least one mutated allele. No associations were found between F5G1691A/F2G20210A, unprovoked VTE or recurrence (p > .05). CONCLUSIONS: Our study provides new data on genetic risk factors for VTE in the very elderly people. Whether identification of hereditary thrombophilia in elderly patients may influence patient's management in this age group remains unanswered.

Prevalence of factor V Leiden and prothrombin G20210A mutation in a large French population selected for nonthrombotic history: geographical and age distribution.

Among inherited risk factors for venous thrombosis, the most common are the FV-G1691A and FII-G20210A polymorphisms. The FV-G1691A polymorphism is preferentially observed in Europe, with differences between European countries. The FII-G20210A polymorphism is observed all over the world. The study was designed to compare the prevalence of the FV-G1691A and FII-G20210A polymorphisms in a large French population of unrelated individuals with no thrombotic disease history and to determine the age and geographical distributions. Over a period of 18 months, 6154 individuals were included throughout France and FV-G1691A and FII-G20210A polymorphisms were determined. The FV-G1691A prevalence was 3.84% (95% confidence interval 3.35-4.33) and the FII-G20210A prevalence was 3.07% (95% CI 2.63-3.51). A north-east/south-west gradient was observed in the FV-G1691A geographical distribution. No difference was observed in the geographical distribution of FII-G20210A polymorphism nor in the age distribution of the two polymorphisms. The prevalence of the two polymorphisms was similar whatever the blood group (O or non-O). Plasma D-dimers were significantly higher in healthy individuals with FV-G1691A but not in individuals with FII-G20210A. Thirty percent of variation in plasma prothrombin level was explained by environmental factors (serum cholesterol, age, oral contraception, hormonal replacement therapy, body mass index, sex) and genetic factors (FII-G20210A). As expected, individuals with FII-G20210A displayed higher plasma prothrombin level compared with individuals with wild type. However, this was not associated with a modification of the fibrin clot elastic modulus. This study shows a differential distribution of the two polymorphisms among the French territory. These polymorphisms confer a very mild hypercoagulable state as shown by the limited increased in basal D-dimers in mutated FV-G1691A populations and only a trend that does not reach statistical significance for FII-G20210A population.

Coagulation disorders in patients with venous malformation of the limbs and trunk: a case series of 118 patients.

OBJECTIVE: To investigate the clinical characteristics of venous malformation of the limbs and trunk and known but poorly appraised associated coagulation disorders. Venous malformations are ubiquitous, slow-flow vascular anomalies known to be occasionally painful because of thrombotic episodes inside the lesion. DESIGN: Large case series, with screening of accepted standard coagulation tests. SETTING: Ambulatory multidisciplinary clinics for vascular anomalies. PATIENTS: This 2-year study (2003-2005) included 118 patients with clinical, radiological, and biological features informative for better defining venous malformation and associated coagulation abnormalities. MAIN OUTCOME MEASURES: The primary outcome was coagulation disorders associated with VM. Secondary measures include anatomic location, extent of lesion, localized pain, and impaired motion. RESULTS: The mean age of patients was 27 years, and there was a female preponderance of 64%. The venous malformation involved the upper extremity, lower extremity, and trunk in 30%, 58%, and 36% of patients, respectively; it was plurifocal in 22%. Intralesional pain (in 92% of patients) had a higher frequency in female (63%) than in male (47%) patients. Tissular involvement concerned the skin (65%), muscle (73%), bone (13%), joints (12%), and viscera (9%). According to our severity scoring system, cases of less gravity had a score of 2 or 3 (52%), cases of intermediate severity had a score of 4 or 5 (32%), and cases of major severity had a score of 6 to 9 (10%). The most frequent blood coagulation abnormality was a high plasma D-dimer level (> 0.5 microg/mL) (58% of patients), which was correlated with muscle involvement and high severity score and was more frequent in women. The factor VIII-von Willebrand factor complex was documented in 84 patients, and plasma von Willebrand factor level was decreased (<60%) in 23 (27%) of them; 10 of the 84 patients (12%) had more notably decreased levels (<50%). CONCLUSIONS: This study of a large case series of patients with pure venous malformation in the limbs and/or trunk highlights muscle involvement and frequency of pain. It validates that coagulation disorders, present in 58% of our patients, create thrombotic painful events. Under certain circumstances, these disorders entail a risk of hemorrhage because of the progression of localized intravascular coagulopathy to disseminated intravascular coagulopathy.

Recombinant activated factor VII decreases bleeding without increasing arterial thrombosis in rabbits.

PURPOSE: To compare the effects of recombinant activated factor VII (rFVIIa) and platelet-rich plasma (PRP) in an experimental model of bleeding and arterial thrombosis. METHODS: The Folts model was used in 60 rabbits. After anesthesia, the carotid artery was exposed and a 75% stenosis was induced. A compression injury of the artery triggered a series of cyclic flow reductions (CFRs). After counting baseline CFRs, animals were assigned randomly to one of four groups (n = 15 in each): control, PRP, rFVIIa and placebo. Control animals received 10 mL.kg(-1) of saline while 10 mL.kg(-1) of a hydroxyethyl starch solution (200,000/6%/0.5) were infused in the three other groups. CFRs were measured again, followed by treatment with PRP, rFVIIa or placebo and by a final measurement of CFRs. At the end of each observation period, an ear immersion bleeding time (BT) was measured and a blood sample was drawn for the evaluation of hematological variables. Microvascular bleeding was evaluated at the end of the experiment in grams of blood shed from liver and spleen sections. Results are presented as median (range). RESULTS: rFVIIa shortened the BT and decreased microvascular bleeding as compared with placebo [60 (35-100) sec vs 110 (50-140) sec, P = 0.0019 and 9 (4-24) g vs 17 (5-28) g, P = 0.002, respectively]. rFVIIa did not increase CFRs [3(0-9) vs |(0-5), P = 0.11]. CONCLUSION: rFVIIa led to a decrease in BT and microvascular bleeding but did not significantly affect arterial thrombosis in rabbits.

Platelet activation and aggregation profile in prolonged external ventricular support.

BACKGROUND: Platelet function plays a major role in the understanding of thromboembolic events in prolonged mechanical support. We studied the platelet activation, platelet aggregation profile, and efficacy of aspirin in patients in whom an external ventricular assist device had been implanted. PATIENTS AND METHODS: Fifteen patients were studied prospectively up to 6 weeks after implantation of the same type of ventricular assist device. Platelet function was studied weekly before daily aspirin administration. Aspirin efficacy was tested ex vivo by measuring platelet aggregation triggered by arachidonic acid. Flow cytometry was used to quantify the spontaneous and induced (adenosine diphosphate stimulation) expression of glycoproteins alphaIIbbeta3, Ibalpha, and CD62P on platelet membranes. The plasma levels of von Willebrand factor (von Willebrand factor activity and von Willebrand factor antigen) and fibrinogen were also determined. RESULTS: Six of the 15 patients (26%) maintained an arachidonic acid-induced platelet aggregation despite daily aspirin treatment (250 mg). CD62P values remained increased during a 5-week postoperative period. Spontaneous levels of glycoproteins alphaIIbbeta3 and Ibalpha on platelet membranes remained within a normal range with a preserved reactivity. The plasma levels of fibrinogen and von Willebrand factor remained increased during the entire study period. CONCLUSION: In patients with an implanted external ventricular assist device, the platelet activation profile displays a persistent activation with a preserved reactivity associated with a persistent high inflammatory state and endothelial activation.

The effects of a polymerized bovine-derived hemoglobin solution in a rabbit model of arterial thrombosis and bleeding.

UNLABELLED: Hemoglobin-based oxygen carriers (HBOCs) have been developed primarily for their oxygenating function and possible use as an alternative to red blood cells during surgery or after major trauma. However, their effect on hemostasis has not been studied extensively. We compared the effects on hemostasis of bovine-derived hemoglobin solution (HBOC-201) with gelatin solution and saline infusion in an experimental model of arterial thrombosis and bleeding. After anesthesia, the Folts model was constructed in 30 rabbits. The common carotid artery was exposed, and a 60% stenosis was induced. A compression injury of the artery was then produced, which triggered a series of cyclic episodes of thrombosis (cyclic flow reductions [CFRs]). After the number of baseline CFRs was counted, animals were assigned randomly to one of three groups (n = 10 each): saline (control), gelatin, or HBOC-201 solution. The effect of studied solutions was observed by recording the number of CFRs during another period and was compared with that of saline. Ear immersion bleeding time was recorded after each CFR period. Gelatin and HBOC-201 had similar effects, manifested by significantly decreased CFRs (from median of 7 to 1 and 6 to 1, respectively) and significantly lengthened bleeding time (from 88 to 98 s and 81 to 102 s, respectively; P < 0.05). Saline infusion had no significant effect on CFRs or bleeding time. HBOC-201 and gelatin had similar effects marked by a reduction in the arterial thrombosis rate and increased bleeding time in rabbits. IMPLICATIONS: In a rabbit thrombosis and hemorrhagic model, a polymerized bovine-derived hemoglobin solution and a gelatin solution infusion decreased arterial thrombosis and lengthened bleeding time.

Coagulation abnormalities associated with extensive venous malformations of the limbs: differentiation from Kasabach-Merritt syndrome.

Confusion in the nomenclature of vascular malformations has been a major obstacle to the understanding of these conditions, so that misdiagnosis and treatment inconsistencies are common. Coagulation abnormalities occurring in combination with venous malformations (VM) have been misdiagnosed as Kasabach-Merritt syndrome (KMS), despite marked differences in clinical features, pathology and treatment. A homogenous group of 24 patients with diffuse limb VM was entered into a retrospective chart review study. The VM affected an upper limb in 12 patients, a lower limb in 10 and both in two. Localized intravascular coagulation (LIC) was characterized by a decrease in fibrinogen (0.5-1 g/l), an increase in d-dimers (2-64 micro g/ml) and presence of soluble complex of fibrin (+ to +++). Platelet counts were normal or slightly decreased. Higher VM severity scores were associated with more severe LIC. A number of events such as sclerotherapy, surgery, bone fracture, prolonged immobilization and pregnancy or menstruation triggered conversion of the LIC to disseminated intravascular coagulation (DIC), with bleeding related to factor consumption and multiorgan failure related to disseminated microvascular thrombosis. Clinical symptoms associated with worsening of LIC were pain, thrombosis and bleeding at wound sites or during surgery. None of the patients had the large ecchymotic and inflammatory tumours seen in KMS. Graded permanent elastic compression with heparin therapy was the only effective treatment. In conclusion, VM-associated LIC is a distinctive lifelong coagulopathy that must be differentiated from KMS, which is characterized by platelet trapping within a vascular tumour of infancy. The treatment of the two conditions is very different.

Erythropoietin and granulocyte colony-stimulating factor increase plasminogen activator inhibitor-1 release in HUVEC culture.

UNLABELLED: Recombinant human erythropoietin (rHuEPO) is considered to be a mitogenic and chemotactic agent in cultured endothelial cells (ECs). The effect of recombinant granulocyte-macrophage (rGM-CSF) and granulocyte (rG-CSF) colony-stimulating factors on the proliferation of human umbilical vein endothelial cells (HUVECs) has been controversial. METHODS: HUVEC proliferation and the release of endothelial markers in HUVEC culture stimulated by rHuEPO, rGM-CSF and G-CSF were measured. RESULTS: We found the dose-dependent stimulating effect of rHuEPO and rGM-CSF on HUVEC proliferation, but we did not achieve this with rG-CSF. rHuEPO like rG-CSF was an effective agent in stimulating the plasminogen activator inhibitor (PAI)-1 release from HUVECs to a cultured medium, while rGM-CSF failed. CONCLUSION: We suggest that rHuEPO showed prothrombotic changes in HUVEC culture. Our results support the idea of suspected rHuEPO direct prothrombotic role in haemodialysed patients treated with rHuEPO.