Detection of direct oral anticoagulants with the dilute Russels viper venom time – observations in a real life setting

Background

The detection of direct oral anticoagulants (DOACs) in emergency settings still remains challenging, especially when dedicated anti-Xa or anti-IIa tests are not readily available or the specific DOAC is unknown. The dilute Russel's viper venom time (dRVVT) is widely known in lupus anticoagulant (LA) testing and may also provide helpful information regarding the residual antithrombotic activity of DOACs. Yet real world data describing the effect of DOACs on the dRVVT is scarce.

Objective

The study aimed to evaluate the sensitivity and specificity of dRVVT for different DOAC plasma levels.

Methods

A total of 80 patients were recruited – 20 patients for each approved DOAC (apixaban, edoxaban, rivaroxaban and dabigatran). Blood plasma was sampled before (baseline), 6 and 12 hours after DOAC-intake and at plasma peak time. DRVVT was measured using the LA1 screening assay for lupus anticoagulant. Plasma levels were measured by calibrated anti-Xa or anti-IIa tests. Additionally, activated partial thromboplastin time (aPTT) and prothrombin time (PT) were measured.

Results

All DOACs significantly prolonged the dRVVT. The effects were more pronounced at higher DOAC plasma levels. The area under the receiver operating characteristic (ROC) curve regarding a plasma level cut-off of 30 ng/ml was 0.92 (95% confidence interval (CI) 0.823 to 1.00) for apixaban, 0.97 (95% CI 0.902 to 1.00) for edoxaban, 0.87 (95% CI 0.649 to 1.00) for rivaroxaban and 0.96 (95% CI 0.871 to 1.00) for dabigatran.

Conclusion

A dose dependent effect of all approved direct oral anticoagulants (DOACs) on the dilute Russel's viper venom time (dRVVT) was documented in our real world setting, while relevant DOAC plasma levels did not affect standard coagulation tests. The negative predictive value for the dRVVT was high even at low DOAC plasma levels. The dRVVT could therefore be helpful to rule out relevant antithrombotic plasma activity caused of DOACs in emergency situations.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Universität Leipzig Figure 1. ROC curves

Kardiochirurgische Eingriffe bei schweren Blutungsdiathesen

Cardiovascular diseases are the most common disorder in the developed countries. Invasive cardiological and cardiosurgical techniques are known therapies.Yet, patients with severe hereditary haemorrhagical diseases (haemophilia, rare deficiencies of coagulation factors) have an increased bleeding risk by the use of anticoagulants. Therefore, the treatment of these patients requires a concomitant therapy.

This article shows eight patients with a severe bleeding diathesis and cardiosurgical interventions in the years 2006 to 2011. This case report shall demonstrate that an adequate therapy can be accomplished with the help of a good cooperation between haemostaseologists and colleagues of the cardioinvasive/ cardiosurgical disciplines.

Von-Willebrand-Syndrom Typ 1 und Schwangerschaft

The von Willebrand-Jürgens syndrome (VWJS) type 1 is a common hereditary bleeding disorder with a bleeding tendency located especially in the mucous membranes. Women suffering from VWJS type 1 show menorrhagia and prolonged postoperative bleedings. During pregnancy the clinical presentation varies by the increase of the von Willebrand factors.

In this article the laboratory findings and the clinical presentation of patients with VWJS during pregnancy was examined. The necessity of interventions during pregnancy and at the time of delivery was under consideration.

Diagnose angeborener Störungen der Thrombozytenfunktion

Angeborene Störungen der Thrombozytenfunktion sind eine heterogene Gruppe von Erkrankungen, die oft erst bei Auftreten von Blutungen erkannt werden. Im klinischen Bereich haben sich nur wenige Methoden zur Diagnose und Klassifizierung von angeborenen Thrombozytenfunktionsstörungen bewährt. Für eine rationelle Diagnostik ist ein stufenweises Vorgehen empfehlenswert. Anamnese und klinische Untersuchung sind Grundvoraussetzungen. Das von-Willebrand-Syndrom und andere plasmatische Gerinnungsstörungen sollten vor einer spezifischen Thrombozytenfunktionsdiagnostik immer ausgeschlossen werden. Die Bestimmung von Zahl, Größe, Volumen (MPV) und Morphologie der Thrombozyten erlauben Rückschlüsse auf die zu Grunde liegende Störung.

Die PFA-100®-Verschlusszeit eignet sich als Screening zum Ausschluss schwerer Thrombozytenfunktionsstörungen. Die Aggrego metrie ermöglicht die Untersuchung zahlreicher Aspekte der Thrombozytenfunktion. Die Durchflusszytometrie ist zur Diagnose von Thrombasthenie Glanzmann, Bernard-Soulier- Syndrom und Freisetzungsstörungen geeignet. Molekulargenetische Untersuchungen können die Verdachtsdiagnose bestätigen oder zum Nachweis nicht beschriebener Defekte verwendet werden. Hier wird die ungekürzte Version der inter -disziplinären Leitlinie* präsentiert.

Genetic Predisposition to Bleeding during Oral Anticoagulant Therapy: Evidence for Common Founder Mutations (FIXVal-10 and FIXThr-10) and an Independent CpG Hotspot Mutation (FIXThr-10)

The recent discovery of five patients with coumarin sensitive FIX-variants due to a missense mutation in the FIX propeptide, either Ala-10Val or Ala-10Thr, has highlighted a novel type of genetic predisposition to bleeding during oral anticoagulant therapy (OAT). In the present study, we report six additional patients with such FIX variants. Haplotype analysis of FIX polymorphisms revealed a founder effect in the five German and Swiss patients with the Val-10 variant. Also, four Thr-10 variants detected in Germany, Switzerland and Great Britain derived from a common founder. Two Thr-10 variants from USA showed an independent de novo origin at a CpG dinucleotide that in general represents a mutation hotspot. These findings implicate the existence of additional subjects with corresponding variants in the populations of various countries. Even though the rare occurrence of these variants does not justify a general aPTT screening during OAT, it is recommended to monitor each bleeding event during OAT in males in order to exclude a genetic predisposition to bleeding by means of the following testing strategy: a) aPTT-testing in each bleeding complication of male patients during OAT, b) if aPTT is disproportionately prolonged, determination of FIX:C, and c) if FIX:C is disproportionately decreased as compared to FII:C, FVII:C and FX:C, sequencing of exon 2 of the FIX gene. This strategy will provide a cost-effective and safe procedure to identify patients that carry the FIX variants. Moreover, such a strategy accumulates data about the prevalence of these FIX mutations in a given population.

Variability of cut-off values for the detection of lupus anticoagulants: results of an international multicenter multiplatform study

Essentials Between-lab variations of cut-off values in lupus anticoagulant detection are unknown. Cut-off values were calculated in 11 labs each testing plasma from 120 donors with 3 platforms. Major variation was observed even within the same platform. Cut-off values determined in different labs are not interchangeable.

SUMMARY

Background Cut-off values for interpretation of lupus anticoagulant (LA) detection are poorly investigated. Aims (i) To assess whether results from healthy donors were normally distributed and (ii) the between-laboratories differences in cut-off values for screening, mixing and LA confirmation when calculated as 99th or 95th centiles, and (iii) to assess their impact on the detection rate for LA. Methods Each of 11 laboratories using one of the three widely used commercial platforms for LA detection was asked to collect plasmas from 120 healthy donors and to perform screening, mixing and LA confirmation with two methods (activated partial thromboplastin time [APTT] and dilute Russell viper venom [dRVV]). A common set of LA-positive or LA-negative freeze-dried plasmas was used to assess the LA detection rate. Results were centralized (Milano) for statistical analysis. Results and conclusions (i) Clotting times or ratios for healthy subjects were not normally distributed in the majority of cases. The take-home message is that cut-off values should be determined preferably by the non-parametric method based on centiles. (ii) There were relatively large inter-laboratory cut-off variations even within the same platform and the variability was marginally attenuated when results were expressed as ratios (test-to-normal pooled plasma). The take-home message is that cut-off values should be determined locally. (iii) There were differences between cut-off values calculated as 99th or 95th centiles that translate into a different LA detection rate (the lower the centile the greater the detection rate). The take-home message is that cut-off values determined as the 95th centile allow a better LA detection rate.

Clot waveform analysis in patients with haemophilia A

Clot waveform analysis extends the interpretation of aPTT measurement curves. The curve is mathematically processed to obtain information about fibrin formation kinetics including semiquantitative determination of thrombin, prothrombinase and tenase activity.

PATIENTS, METHOD

In this study the feasibility of clot waveform analysis for monitoring of haemophilia A was investigated using blood samples from healthy controls as well as haemophilia A patients under various clinical conditions.

RESULTS

Thrombin, prothrombinase and tenase activity show a high correlation to factor VIII levels. Tenase activity was found to exhibit a linear relationship to factor VIII levels over a very large concentration range and was able to discriminate patients with severe, moderate and mild haemophilia.

CONCLUSION

Clot waveform analysis is an easy, fast and cheap method to access disturbances in clot formation and can be done without any additional measurements beside an aPTT.

[Therapy of inherited diseases of platelet function. Interdisciplinary S2K guideline of the Permanent Paediatric Committee of the Society of Thrombosis and Haemostasis Research (GTH e. V.)]

Inherited disorders of platelet function are a heterogeneous group. For optimal prevention and management of bleeding, classification and diagnosis of the underlying defect are highly recommended. An interdisciplinary guideline for a diagnostic approach has been published (AWMF # 086-003 S2K; Hämostaseologie 2014; 34: 201-212). Underlying platelet disorder, platelet count, age and clinical situation modify treatment. Exclusive transfusion of platelet concentrates may be inappropriate as potentially adverse effects can outweigh its benefit. A stepwise and individually adjusted approach for restitution and maintenance of haemostasis is recommended. Administration of antifibrinolytics is generally endorsed, but is of particular use in Quebec disease. Restricted to older children, desmopressin is favourable in storage pool disease and unclassified platelet disorders. Although licensed only for patients with Glanzmann thrombasthenia and alloantibodies, in clinical practice rFVIIa is widely used in inherited platelet disorders with severe bleeding tendency. This guideline aims at presenting the best available advice for the management of patients with inherited platelet function disorders.

[Cardiac surgery in severe haemorrhagical diseases]

Cardiovascular diseases are the most common disorder in the developed countries. Invasive cardiological and cardiosurgical techniques are known therapies. Yet, patients with severe hereditary haemorrhagical diseases (haemophilia, rare deficiencies of coagulation factors) have an increased bleeding risk by the use of anticoagulants. Therefore, the treatment of these patients requires a concomitant therapy. This article shows eight patients with a severe bleeding diathesis and cardiosurgical interventions in the years 2006 to 2011. This case report shall demonstrate that an adequate therapy can be accomplished with the help of a good cooperation between haemostaseologists and colleagues of the cardioinvasive/cardiosurgical disciplines.

[Von Willebrand disease type 1 and pregnancy]

The von Willebrand-Jürgens syndrome (VWJS) type 1 is a common hereditary bleeding disorder with a bleeding tendency located especially in the mucous membranes. Women suffering from VWJS type 1 show menorrhagia and prolonged postoperative bleedings. During pregnancy the clinical presentation varies by the increase of the von Willebrand factors. In this article the laboratory findings and the clinical presentation of patients with VWJS during pregnancy was examined. The necessity of interventions during pregnancy and at the time of delivery was under consideration.

Platelet-dependent coagulation assays for factor VIII efficacy measurement after substitution therapy in patients with haemophilia A

FVIII therapy for haemophilia A is safe and effective, with the problem of individually sufficient efficacy unsettled. Routine one-stage clotting assays and tests employing chromogenic substrates poorly detect individual haemostatic effects of FVIII due to artificial test conditions. In particular, the use of cell-free and diluted plasma samples neglect the crucial role of platelets for thrombin and fibrin formation. To optimize FVIII substitution therapy, we measured in 40 patients with severe to mild haemophilia A before and after FVIII substitution the FVIII activity in cell-free plasma samples using a one-stage clotting assay as well a chromogenic substrate assay and compared the data with those obtained with cell-based coagulation tests, i.e. thrombin generation in platelet-rich plasma (PRP) and thromboelastography (TEG) in samples of citrated whole blood (WB). To determine the maximum ex vivo haemostatic effect we added 1 unit/ml of FVIII to samples of PRP and WB and measured the maximum thrombin generation in the thrombin generation test (TGT) and the maximum clot firmness (MCF) in TEG. After FVIII substitution we observed a nearly linear relation between the individual FVIII activities administered to the patients and the activities measured in the plasma samples. However, data obtained with TGT and TEG revealed a high inter-individual variation and a very poor correlation to the administered FVIII activity. Actually, it could be shown that FVIII substitution yielding in a FVIII plasma activity of about 30% is sufficient to get an ex vivo haemostatic effect of more that 90% as measured by maximum thrombin generation and MCF. FVIII substitution up to a plasma activity of more than 90% did not further enhance the haemostatic effect. Our data clearly demonstrate that the haemostatic effect of FVIII is not only dependent on the activity that is measured in plasma but also depends on the interplay between coagulation and blood cells, in particular with platelets. The use of cell-based coagulation tests such us TGT or TEG may help to optimize FVIII therapy by determining the individual FVIII dosage that produces a maximum haemostatic effect.

Evaluation of the pharmacokinetics of dalteparin in patients with renal insufficiency

The pharmacokinetics of the low-molecular weight heparin (LMWH), dalteparin, was evaluated after a single intravenous bolus injection of 50 IU anti-Xa/kg in 8 healthy volunteers, 8 patients with moderate/severe renal failure (Cl(crea) 13.1-56.5 ml/min) and 8 hemodialysis patients. Venous blood samples were taken over a 1-day period to determine anti-Xa activity, anti-IIa activity and plasma levels of free tissue factor pathway inhibitor (free TFPI). Plasma anti-Xa and anti-IIa activities were measured using chromogenic assays and free TFPI levels using an ELISA technique. The anti-Xa clearance was significantly decreased (p < 0.05) in both groups with renal insufficiency when compared with healthy volunteers. There was a positive correlation between creatinine clearance and anti-Xa clearance in the healthy volunteers and patients with moderate/severe renal failure. The anti-Ila activity was characterized by 3- to 4-fold lower plasma concentrations and faster elimination compared with the anti-Xa activity. In patients with moderate/severe renal failure the elimination of anti-lla was only slightly decreased, whereas in hemodialysis patients anti-Ila clearance was significantly decreased (p < 0.01). There was no correlation between creatinine clearance and anti-IIa clearance. The baseline mean free TFPI plasma levels in the two groups with renal insufficiency were significantly higher (p < 0.01) than in healthy volunteers. Dalteparin administration induced a transient, 6.0- to 8.1-fold increase in the free TFPI values in the three study groups. Dalteparin induced an increase in C(max) and AUC(0 - infinity) values of free TFPI in the two groups with renal insufficiency that was higher than in healthy volunteers. No bleeding complications occurred during the study. In conclusion, this is the first report showing retarded elimination of dalteparin and enhanced free TFPI plasma levels induced by a LMWH in patients with renal insufficiency.

Impact of the Thr789Ala variant of the von Willebrand factor levels, on ristocetin co-factor and collagen binding capacity and its association with coronary heart disease in patients with diabetes mellitus type 2

A Thr789Ala variant in the von Willebrand Factor (vWF) gene is associated with increased vWF plasma concentrations and might therefore affect the risk of coronary heart disease (CHD) in the general population. Patients with type 2 diabetes have an increased risk for premature atherosclerosis and are characterized by alterations of the coagulation system. However, it is not known whether the Thr789Ala variant in the vWF gene contributes to the increased CHD risk in patients with type 2 diabetes. We therefore investigated the potential relationship between the Thr789Ala variant in the vWF gene and the occurrence of CHD in 356 patients with type 2 diabetes, either with (DM+/CHD+, n = 204) or without evidence for CHD (DM+/CHD-, n = 152). In addition, two control groups without type 2 diabetes, with (DM-/CHD+, n = 22) or without CHD (DM-/CHD-, n = 100), were investigated. Individuals with the vWF Thr789Ala variant have significantly higher von Willebrand factor plasma concentrations (p < 0.001). In addition, ristocetin co-factor was significantly increased in vWF Thr789Ala variant carriers (p < 0.05). Ristocetin co-factor levels and collagen binding capacity were also increased in individuals affected with either type 2 diabetes, CHD or both (DM+/CHD+, DM+/CHD-, DM-/CHD+) as compared to healthy controls (DM-/CHD-) (p < 0.001). However, we did not find an association between the vWF Thr789Ala variant and the occurrence of CHD in patient with type 2 diabetes (p = 0.34). In conclusion, although the Thr789Ala vWF gene variant is associated with increased plasma concentrations of vWF, ristocetin co factor levels and collagen binding capacity in patients with type 2 diabetes and CHD, a direct effect of this variant on the occurrence of CHD in patients with type 2 diabetes, could not be detected.

Aspirin resistance in secondary stroke prevention

BACKGROUND

We investigated the platelet function in stroke patients treated with aspirin [acetylsalicylic acid (ASA)] for secondary stroke prevention during a follow-up period of 1 year.

METHODS

In this prospective study 291 patients with first initiated aspirin therapy (300 mg/day) for secondary stroke prevention were included. Platelet aggregation measurements were performed 24 h, 3, 6, and 12 months after starting medication.

RESULTS

Twenty-one of 291 patients (7.2%) were identified as primary ASA-non-responders (initial insufficient platelet inhibition) and 4.1% as secondary ASA-non-responders (insufficient platelet inhibition during follow-up). There were no significant differences between ASA-responders and ASA-non-responders concerning age, gender, risk factors, and stroke characteristics.

CONCLUSION

Aspirin resistance in stroke patients is not uncommon. The clinical usefulness of routine platelet function tests needs to be proved by further trials.

[Factor VIII activity in patients with central retinal vein occlusion in comparison to patients with a history of pelvic and lower limb venous thrombosis and a healthy control group]

BACKGROUND

High factor VIII activity levels increase the risk of venous thromboembolism. This study was carried out to investigate the association between factor VIII activity and central retinal vein occlusion (CRVO) in comparison to patients with a history of venous thrombosis and a healthy control group.

PATIENTS AND METHODS

We examined the factor VIII activity in 62 patients with CRVO, 67 patients with venous thrombosis and 107 healthy individuals. The study measure employed for factor VIII activity was a one-stage clotting assay.

RESULTS

53.2 % of the patients with CRVO had an elevated factor VIII activity of more than 150 % (> 150 IU/dl). 78.5 % of the patients with venous thrombosis and 19.7 % of the healthy control group had an elevated factor VIII activity (> 150 IU/dl).

CONCLUSIONS

Elevated factor VIII activity is likely to have an influence on the pathogenesis of the central retinal vein occlusion.

Differences in platelet activation by prolactin and leptin

Hormones such as prolactin and leptin have recently been recognized as potent platelet aggregation co-activators, and have therefore been postulated as an additional risk factor for both arterial and venous thrombosis. Clinical situations exist that are known to be associated with higher leptin and/or prolactin levels (obesity, pregnancy, prolactinomas and anti-psychotic therapy respectively) and increased venous thrombosis or atherosclerosis risk. Therefore, we compared the impact of both hormones on platelet activation in vitro and in vivo. First, we investigated platelet aggregation and P-selectin expression after stimulation with 1,000 mU/l prolactin or 100 ng/ml leptin in five healthy volunteers in vitro. Prolactin revealed significant higher levels of P-selectin expression and platelet aggregation than leptin in all subjects. We also compared the correlation of prolactin and leptin values with the P-selection expression on platelets. Previously, we detected a significant correlation between prolactin values and ADP-stimulated P-selectin expression on platelets in pregnant women, patients with pituitary tumours, and patients on anti-psychotic therapy. In contrast, leptin did not correlate with P-selectin expression in all subject groups investigated. However, leptin correlated with body mass index in the subjects investigated. Our data indicate that prolactin has a stronger effect on platelet activation as leptin in vitro and in vivo. Moreover, our data suggest that the stronger effect of prolactin on ADP-stimulated platelet aggregation, compared to leptin, depends on higher stimulation of CD62p expression by prolactin.

Prolactin receptor signaling during platelet activation

Prolactin is a newly recognized platelet coactivator that functions through potentiation of ADP-induced platelet activation. However, the possible association between hyperprolactinemia and venous thromboembolism (VTE) has not been systematically investigated up to now; prolactin signaling mechanisms in platelets still need to be elucidated. In this study, plasma prolactin levels in healthy subjects and patients with VTE were determined, demonstrating that patients with VTE and no other congenital risk factors had significantly increased plasma prolactin levels. Moreover, prolactinoma patients demonstrated a higher incidence of VTE than the general population. To elucidate the molecular mechanisms for the development of venous thrombosis, prolactin receptor signaling during platelet activation was investigated with a focus on ADP-stimulated G-protein-regulated signaling pathways. The short isoform of prolactin receptors was detected on platelets. Signaling through this receptor, although not directly linked to Gq-proteins, substitutes for Gq-protein regulated signaling pathways involved in platelet activation. We identified protein kinase C, a well-established signaling molecule in platelet activation, as a target molecule for prolactin signaling pathways in human platelets. Our findings indicate that hyperprolactinemia may be an important novel risk factor for VTE, suggesting that its thrombogenic effect may be mediated through enhanced platelet reactivity. Revealing the molecular mechanisms of prolactin signaling will allow the design of new antithrombotic therapies.

The interleukin-1 polymorphism, smoking, and the risk of periodontal disease in the population-based SHIP study

Several studies have shown a role for interleukin-1 gene cluster polymorphisms in the risk assessment for periodontal diseases. In the Study of Health in Pomerania (SHIP), 3148 subjects were randomly selected from the population and assessed for a broad range of diseases and environmental/behavioral risk factors. From the complete study group in the age 40 to 60 years, N = 1085 subjects were genotyped for the interleukin-1 genotype composite polymorphism in relation to periodontal parameters. The study objective was to elucidate the gene-environment interaction between the risk factors smoking and IL-1 polymorphism. An increased risk of periodontal disease was found for IL-1 genotype-positive smokers: odds ratio adjusted for age, sex, education, and plaque OR = 2.50 (95% C.I. 1.21 to 5.13; p = 0.013). This was not the case with subjects who never smoked: OR = 1.09 (0.73-1.62; p = 0.676). These results support the hypothesis of gene-environmental interaction in periodontitis.

Absence of compensatory platelet activation in patients with severe haemophilia, but evidence for a platelet collagen-activation defect

Severe haemophilia is a serious, haemorrhagic disorder of the plasmatic coagulation system. In this study we investigated, whether 'compensatory' activation of the platelet coagulation system occurs in this situation. Platelet function was investigated with aggregation, adhesion and flow cytometric assays. In addition, we performed clot and platelet plug formation tests and determined endogenous thrombin potentials in patients with severe haemophilia A or B; results were compared to those of healthy controls. Platelet aggregation in response to stimulation with ADP, ristocetin and epinephrine was similar in patients and controls; aggregation in response to collagen was reduced significantly in haemophiliacs. Flow cytometric analysis of P-selectin (CD 62P) and CD 63, of the conformationally changed GP IIb/IIIa with PAC 1 and of thrombospondin bound to CD 36 (GP IV) was performed at baseline and post stimulation. Baseline expression of all markers was similar in haemophiliacs and controls. After stimulation of the platelet thrombin receptors with the thrombin receptor activating peptide (TRAP) 6, the surface expression of all markers increased significantly; again, the expression was similar in haemophiliacs and controls. With thrombelastography and PFA 100 analysis, clot formation under low shear and platelet plug formation under high shear is measured. Both test results revealed a significantly reduced clot and platelet plug formation capacity in severe haemophiliacs. Our results did not reveal signs of enhanced platelet preactivation in haemophiliacs, indicating that baseline platelet reactivity in severe haemophilia remains in a neutral state, despite the severely haemorrhagic condition. As expected, both thrombin and clot formation capacities were impaired significantly in severe haemophilia. The reduced response to collagen-based platelet stimulation tests is indicative of a concomitant platelet function defect. This defect probably contributes to the intensity of bleeding events in patients with severe haemophilia.

Paradoxical hyperfibrinolysis is associated with a more intensely haemorrhagic phenotype in severe congenital haemophilia

To elucidate potential causes for differing bleeding phenotypes of haemophilic patients of identical degree of coagulation factor deficiency, we investigated 21 male patients with severe haemophilia. Median annual coagulation factor demand and the extent of haemophilic arthropathy were used to discriminate between intensely and less intensely haemorrhagic phenotypes. Haemophiliacs with a median annual coagulation factor demand of 800 IU per kg bodyweight or more and with three or more joints affected by haemophilic arthropathy represented the intensely haemorrhagic phenotype group; all other patients comprised the less intense group. The discriminator values represent the respective medians of the overall group. The results of activated partial thromboplastin time, endogenous thrombin potential, pro- and anticoagulant factor analysis did not differ between the two groups. Median tissue-type plasminogen activator concentration (TPA) was elevated significantly in haemophiliacs with an intensely haemorrhagic phenotype, as was the activity of the thrombin-activatable fibrinolysis inhibitor. Median activity of the plasminogen activator inhibitor 1 (PAI 1) and the concentration of TPA-PAI 1 complexes were increased to approximately double those in nonsevere haemophiliacs. Coexistent congenital thrombophilia was found significantly more often in the less intensely haemorrhagic group. Thus, increased stimulation of the fibrinolytic system was associated with a more intensely haemorrhagic phenotype in our patients. We hypothesize that ineffective haemophilic haemostasis in response to trauma evokes a protracted stimulation of the entire haemostatic system, including costimulation of fibrinolysis. The absence of coexistent congenital thrombophilia predisposes to excess stimulation of fibrinolysis, which cannot be downregulated effectively due to the dysfunctional intrinsic pathway. The association of a more intensely haemorrhagic phenotype with a paradoxical hyperstimulation of the fibrinolytic system resembles a vicious circle, where bleeding seems to cause predisposition to more bleeding.

Genetic predisposition to bleeding during oral anticoagulant therapy: evidence for common founder mutations (FIXVal-10 and FIXThr-10) and an independent CpG hotspot mutation (FIXThr-10)

The recent discovery of five patients with coumarin sensitive FIX-variants due to a missense mutation in the FIX propeptide, either Ala-10Val or Ala-10Thr, has highlighted a novel type of genetic predisposition to bleeding during oral anticoagulant therapy (OAT). In the present study, we report six additional patients with such FIX variants. Haplotype analysis of FIX polymorphisms revealed a founder effect in the five German and Swiss patients with the Val-10 variant. Also, four Thr-10 variants detected in Germany, Switzerland and Great Britain derived from a common founder. Two Thr-10 variants from USA showed an independent de novo origin at a CpG dinucleotide that in general represents a mutation hotspot. These findings implicate the existence of additional subjects with corresponding variants in the populations of various countries. Even though the rare occurrence of these variants does not justify a general aPTT screening during OAT, it is recommended to monitor each bleeding event during OAT in males in order to exclude a genetic predisposition to bleeding by means of the following testing strategy: a) aPTT-testing in each bleeding complication of male patients during OAT, b) if aPTT is disproportionately prolonged, determination of FIX:C, and c) if FIX:C is disproportionately decreased as compared to FII:C, FVII:C and FX:C, sequencing of exon 2 of the FIX gene. This strategy will provide a cost-effective and safe procedure to identify patients that carry the FIX variants. Moreover, such a strategy accumulates data about the prevalence of these FIX mutations in a given population.

[Recurrent coumarin necrosis in type II protein S deficiency]

Coumarin necrosis is a rare but clinical very important complication of therapy with coumarin derivatives. We report a patient with congenital protein S deficiency type II, who developed coumarin necrosis during stabilization of phenprocoumon. Diagnostic problems and therapeutic alternatives are discussed considering the recent literature.

Coagulation, fibrinolysis and platelet P-selectin expression in peripheral vascular disease

OBJECTIVES

to examine coagulation, fibrinolysis, and platelet activity in patients with peripheral vascular disease (PVD).

DESIGN

fifty consecutive PVD patients and 50 healthy volunteers. (Prospective comparative study.)

MATERIALS AND METHODS

P-selectin expression in non-fixed, whole blood was measured flow cytometrically on non-stimulated and ADP- and TRAP-6-stimulated samples. Plasma fibrinogen, von Willebrand factor (vWF), tissue plasminogen activator (tPA), and plasminogen activator inhibitor-1 were determined using standard techniques. Disease severity was stratified on the basis of the ankle-brachial pressure index (ABPI) and the angiographic data were assessed using the Bollinger score.

RESULTS

coagulation and fibrinolysis parameters as well as the P-selectin expression on both stimulated and non-stimulated platelets were significantly increased in patients vs controls (all p<0.01). The respective sensitivity and specificity were as follows: P-selectin expression (81%, 94%), vWF (72%, 86%), fibrinogen (64%, 98%), PAI-1 (44%, 90%), tPA (15%, 100%). P-selectin expression on TRAP-6-stimulated MP correlated with disease severity (r=0.40, p<0.01).

CONCLUSIONS

these findings support the concept of ongoing thrombogenesis in the subclinical progression of PVD and demonstrate the high diagnostic sensitivity of flow cytometric analysis of platelet activation.

Factor XIII deficiency and postoperative hemorrhage after neurosurgical procedures

BACKGROUND

Factor XIII is of physiological importance for hemostasis, especially in patients undergoing surgery. It catalyzes the enzymatic cross-linking of fibrin monomers into stable polymers and protects polymers from plasmatic and nonspecific degradation. Postoperative hemorrhage in patients with congenital and acquired Factor XIII deficiencies has been described in various surgical fields. However, there are no data about the incidence and clinical relevance of decreased Factor XIII after neurosurgical procedures. The objective of our study was to investigate the association between Factor XIII deficiency and postoperative hemorrhage after intracranial surgery.

METHODS

A total of 1264 patients who underwent intracranial operations were reviewed retrospectively. Standard coagulation parameters were monitored during the perioperative course in all patients. Factor XIII testing was performed postoperatively in 34 patients in whom coagulopathies were suspected despite normal platelets, fibrinogen, prothrombin, and partial thromboplastin time. Data were analyzed to evaluate the association of Factor XIII deficiency and major postoperative hemorrhage.

RESULTS

In this series of 1264 patients, a total of 20 patients (1. 6%) suffered from a major postoperative hemorrhage. Of the 34 patients with suspected coagulopathies and postoperative Factor XIII testing, 11 had a major postoperative hemorrhage. Normal levels of Factor XIII, defined as more than 60%, were found in 26 of the 34 patients. Factor XIII deficiency, defined as less than 60%, was found in eight patients. All patients with Factor XIII deficiency (n = 8) had a major postoperative hemorrhage. Of the remaining 26 patients with normal Factor XIII levels only three had a postoperative hemorrhage (p < 0.00001, Fisher's exact test).

CONCLUSIONS

Decreased Factor XIII activity may be associated with an increased risk of postoperative hemorrhage after intracranial surgery.

[Activated protein C resistance in patients with central retinal vein occlusion in comparison to patients with a history of deep-vein thrombosis and a healthy control group]

BACKGROUND

The recently described "APC resistance" caused by a mutant form of factor V (factor V Leiden) is the most frequent cause of hereditary thrombosis. This study was carried out to investigate the association between activated protein C resistance and central retinal vein occlusion (CRVO). We evaluated the prevalence of APC resistance in patients with CRVO, patients with a history of deep-vein thrombosis, and a healthy control group.

PATIENTS AND METHODS

We examined 107 patients with CRVO, 112 patients with deep-vein thrombosis and 70 healthy individuals. The test performed was a modified APC-resistance assay using factor V-deficient plasma.

RESULTS

We identified APC resistance in 5.6 % of patients with CRVO and in 5.7 % of the control group. All carriers were heterozygous. In the deep-vein thrombosis group 23.2 % tested positive for APC resistance. Four patients were homozygous and 22 were heterozygous carriers.

CONCLUSION

These results indicate that APC resistance has no major role in the pathogenesis of CRVO. Routine testing for the presence of factor V Leiden mutant in CRVO is not necessary.

[Thrombolysis of an extensive venous thrombosis of the lower body in an anomaly of the vena cava inferior]

HISTORY AND CLINICAL FINDINGS

A 41-year-old man was admitted to hospital for acute pain in the right flank. At first urolithiasis was suspected but excluded by sonography and excretion urography. Computed tomography (CT) was performed because of increasing pain and swelling of the left leg. It showed bilateral thrombosis of the deep leg and pelvic veins as well as of the infrarenal inferior vena cava (IVC) and the right renal vein. The patient's general condition was impaired. The circumference of the left leg was greater than that of the right by 5 cm 15 cm above the knee joint space and both legs had marked varicosities with congestive dermatitis.

INVESTIGATIONS

The concentration of the thrombin-antithrombin complex was 13.4 micrograms/l, D-dimer 124 micrograms/l, prothrombin fragment F1+2 3,5 nmol/l and fibrin monomere 27.7 micrograms/ml, as expression of a manifest thrombosis. CT with contrast medium demonstrated the previously sonographically shown extent of the thrombosis. In addition the hepatic IVC segment was absent. The azygos vein was enlarged and there was an extensive collateral circulation.

TREATMENT AND COURSE

Systemic thrombolysis (streptokinase for 3 days, then urokinase) for 11 days dissolved the thrombi and CT now demonstrated complete recanalization of the caudal deep vein system and the IVC abnormality (absence of hepatic segment). After intravenous thrombolysis oral anticoagulation with phenprocoumon was started and will be continued all the patient's life.

Hämostaseologische Risikoindikatoren im Verlauf der tiefen Venenthrombose und ihre Beziehung zur Entzündungsreaktion (CRP)

In dieser Studie sollte bei Patienten mit tiefer Venenthrombose im Verlauf des akuten Ereignisses und bei ambulanter Nachuntersuchung die Beziehung zwischen bekannten hämostaseologischen Risikoindikatoren der Thrombophilie und der Akute-Phase-Reaktion untersucht werden. 73 Patienten mit phlebographisch gesicherter Venenthrombose wurden am Tag der Klinikaufnahme, am zweiten Tag und bei Entlassung aus dem Krankenhaus untersucht, bei 63 Patienten erfolgte eine ambulante Nachuntersuchung nach Abklingen der akuten Symptomatik. Bestimmt wurden die Parameter Plasminogenaktivator-Inhibitor (PAI), Ristocetin-Kofaktor, Plasminogen, Antithrombin III (AT III), Protein C, Protein S, Fibrinogen und C-reaktives Protein (CRP). Es zeigte sich ein deutlicher Abfall der bei 90% der Patienten pathologisch erhöhten CRP-Werte vom Zeitpunkt der Klinikaufnahme bis zur Entlassung aus dem Krankenhaus, 1/3 der Patienten hatte auch zum Zeitpunkt der ambulanten Nachuntersuchung noch erhöhte CRP-Konzehtrationen >0,5 mg/dl. Diese Patienten hatten eine Häufigkeit pathologisch erhöhter Werte von Fibrinogen (84,2%) und Ristocetin-Kofaktor (47,4%) wie zum Zeitpunkt der Akutveränderung bei Klinikaufnahme. Bei 2/3 der Patienten konnte bei der ambulanten Nachuntersuchung anhand unauffälliger CRP-Werte <0,5 mg/dl eine Akute-Phase-Reaktion ausgeschlossen werden. Diese Patienten hatten zu 49% pathologisch erhöhte Fibrinogenwerte, zu 41 % pathologisch erhöhte PAI-Werte und zu 25% pathologisch erhöhte Ristocetin-Kofaktor-Werte; 39% dieser Patienten mit normalem CRP hatten gleichzeitige Erhöhungen von zwei der drei Parameter Fibrinogen, Ristocetin-Kofaktor und PAI.

Fibrinogen, Ristocetin-Kofaktor und PAI sind auch als Risikoindikatoren arterieller Thrombosen bekannt. Dies führt zu dem Schluß, daß der Pathomechanismus und die Risikokonstellation bezüglich thromboembolischer Ereignisse zwischen arteriellem und venösem System ähnlicher sind als bisher angenommen.

CRP hat sich nach den vorliegenden Ergebnissen als prognostisch wichtiger Risikomarker bei der tiefen Venenthrombose erwiesen. Die vorgelegten Daten können Hinweise darauf geben, daß die Entzündungsreaktion im Pathomechanismus der tiefen Venenthrombose eine kausale und nicht nur sekundäre Rolle spielt. Die prospektive Bedeutung dieser Ergebnisse muß noch durch weitere Untersuchungen geklärt werden.

[Vascular function parameters in idiopathic and quartz-induced progressive scleroderma]

In 15 patients with systemic sclerosis (SS) and 8 patients suffering from silicosis and/or silica dust exposure-associated scleroderma (SAS), various parameters of endothelial cell and platelet function and of blood coagulation and fibrinolysis were studied. In 9 of the 23 patients the values for the von Willebrand factor antigen were increased, and the same applied to the endothelin levels in 8 of 23 patients. Protein C, protein S, anti-thrombin III and tissue plasminogen activator (before and after 10 min venous occlusion) were normal. The plasminogen activator inhibitor, however, was increased in 5 patients. Increased levels of platelet factor 4 and of beta-thromboglobulin were found in 20 patients, while the ADP- and epinephrine-induced platelet aggregation was reduced in 5 patients. No individual patient was found to have a general disturbance of all parameters. The deviations in the parameters of endothelial cell and platelet function and of blood coagulation and fibrinolysis proved to be rather inconsistent. This suggests different functional stages in dependence on the various influential factors. There was no close correlation either with the severity of Raynaud's phenomenon or with the type of SS. In addition, there were no basic differences between SS and SAS. The disturbances occurred with similar frequency and in similar proportions in both disease groups.

Serum enzymes in toxicity of trichloroethylene after subchronic ethanol pretreatment

In order to establish evidence of serum enzyme activities in toxicological long-term experiments alterations of alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) in the serum of rats were investigated after subchronic ethanol pretreatment and following trichloroethylene exposure. Somewhat lower enzyme activities were found in ethanol treated animals than in those who only got water in nearly all cases. Significant ALAT and ASAT decreases occurred after giving higher ethanol concentrations (5% and 10%, v/v) for 30 weeks. It is possible that this fact among other things could be responsible for the only slight enzyme elevations after trichloroethylene in long-term ethanol pretreated rats.