Use of recombinant factor VIIa (NovoSeven) in patients with Glanzmann thrombasthenia.

Recombinant factor VIIa (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark) appears effective and relatively safe for the treatment of bleeding and for surgical prophylaxis in patients with Glanzmann thrombasthenia as reported to the International Registry on rFVIIa and Congenital Platelet Disorders. One of the shortcomings of the Registry data is the heterogeneity of treatment protocol, including dosage, number of doses used, duration of treatment before declaration of failure, and mode of rFVIIa administration (bolus v continuous infusion). The data are not yet sufficient to define optimal regimens for various indications such as the type of bleeding or the type of procedures. The place of this drug compared to platelet transfusion in the overall management of patients with Glanzmann thrombasthenia will need to be determined in relationship to a number of challenges and unresolved issues in the clinical care of these patients. These issues include: how to improve local measures for patients with mucosal bleeds, optimal management of young women during menarche, optimal platelet transfusion regimens for various indications, the relationship between antiplatelet antibodies detected by monoclonal antibody-specific immobilization of platelet antigens (MAIPA) and effectiveness of platelet transfusion, whether there are other biological tests that may correlate with effectiveness of platelet transfusion, and management of pregnancy and delivery regarding antiplatelet immunization.

Long lasting sitting position and haemostasis.

Blood coagulation, fibrinolysis and platelet aggregability were assessed in 8 physicians aged 30-40 years, who had travelled non-stop by car from Salonica to Athens (510 km) and returned to Salonica after 48 h of rest and after administration of 1 g of aspirin. At the end of journey A, platelet aggregability was found to be increased (6 out of 8 persons), AT III was decreased by 30% (p less than 0.001), the F VIII:C / F VIIIR: Ag ratio was decreased (p less than 0.02) and ELT was prolonged. At the end of journey B the findings were the following: platelet aggregation was not affected, the decrease of AT III was not statistically significant and ELT was significantly shortened (p less than 0.005). A common finding of both journeys was the increase of platelet counts at the end (p less than 0.005). The correlation between long lasting sitting and the response of the haemostatic balance is suggested. The influence of aspirin is discussed.

Impaired fibrinolysis as an essential contribution to thrombosis in patients with lupus anticoagulant.

Lupus anticoagulants (LA) are IgG or IgM antibodies against phospholipids which in vivo represent an important thrombophilic factor despite their in vitro anticoagulant activity. We investigated the fibrinolytic system of 20 patients with connective tissue disease and positive LA, compared to a control group of 24 age- and disease-matched patients without LA. There was no statistically significant difference of alpha 2-antiplasmin, plasminogen, fibrinogen, t-PA activity, D-dimers and heparin cofactor II, between the two groups. Although t-PA was uniformly low in both groups, plasminogen activator inhibitor activity (PAI) was significantly higher in LA cases (p less than 0.001). Increased PAI levels represent an inhibitory factor of the fibrinolytic defense mechanism, which together with other functional deviations may contribute to the thrombophilic tendency of LA patients.

Treatment with LMWHs inhibits factor VIIa generation during in vitro coagulation of whole blood.

The role of factor VII and activated factor VII (VIIa) is considered to be crucial in the coagulation process. The efficacy of low molecular weight heparins (LMWHs) in the prevention and treatment of thromboembolic episodes has been established in numerous controlled therapeutic trials. However, the mechanisms of their antithrombotic action are still disputed. Heparins exert their anticoagulant effect by enhancing ATIII inhibitory action on factor Xa and thrombin, which results in decreased factor X activation, prothrombinase formation, prothrombin activation and thrombin generation. Moreover, it is clearly established that both kinds of heparins (unfractionated heparin and LMWHs) induce the release of tissue factor pathway inhibitor (TFPI). Therefore, they are involved indirectly in tissue factor (TF)/factor VIIa complex inhibition by the TFPI/factor Xa complex. Factor VII activation is an essential step in the process of blood coagulation and it plays an important role in thrombogenesis. A method for the measurement of factor VIIa has been recently developed. A study on the effects of antithrombotic drugs, as heparins, on factor VIIa generation might allow to better understand the mechanisms that regulate its activation. We investigated ex vivo the effect of treatment with LMWHs on factor VIIa generation during in vitro coagulation of whole blood in order to clarify if LMWHs interfere with factor VIIa generation.

Factor V Leiden in Greek thrombophilic patients: relationship with activated protein C resistance test and levels of thrombin-antithrombin complex and prothrombin fragment 1 + 2.

We studied 172 Greek patients (72 men aged 44.0 +/- 16.7 years and 100 women aged 46.5 +/- 14.1 years) with an unexplained thrombophilic tendency. One hundred and four apparently healthy persons (63 men aged 34.2 +/- 10.0 years and 41 women aged 37.1 +/- 13.3 years) were included as a control group. We performed the activated protein C resistance (APC-r) test using a clotting test (Chromogenix kit), detection of factor V Leiden using polymerase chain reaction (PCR)-restriction fragment length polymorphisms and measurement of thrombin-antithrombin complexes (TAT) and prothrombin fragment 1 + 2 (F1 + 2) levels with an immunoenzymatic assay. The normal range for the APC-r test (> 2.12) was determined from the controls. The factor V Leiden mutation was found in 31.9% of all the patients tested, in 28.1% of the unrelated patients with documented thrombophilic tendency of unknown origin and in 4.8% of the healthy controls. The APC-r test had a sensitivity of 0.42 and a specificity of 0.91 for the detection of factor V Leiden. Furthermore, we found no significant difference in levels of TAT and F1 + 2 between patients with and without the mutation and there was no correlation between aPC-r values and levels of TAT and F1 + 2.

Comparative effects of synthetic pentasaccharide, low-molecular-weight heparin, unfractionated heparin and recombinant hirudin on the generation of factor VIIa and prothrombin activation after coagulation of human plasma.

We studied the effect of synthetic pentasaccharide, a low-molecular-weight heparin (enoxaparin), unfractionated heparin and recombinant hirudin on the generation of factor VIIa (FVIIa) and prothrombin activation after in-vitro clotting of human platelet-poor plasma. FVIIa was measured with a new clotting assay that uses recombinant tissue factor truncated to interact only with FVIIa. Residual prothrombin was measured using the conventional clotting assay. FVIIa and residual FII were measured in the liquid - called pseudo-serum (psi-serum) - obtained 1 h after clotting of normal platelet-poor plasma. A kinetic study of the generation of FVIIa was also performed. Coagulation was initiated by triggering the extrinsic, the intrinsic and both associated clotting pathways. Levels of FVIIa in the psi-sera (55+/-15, 258+/-18, and 164+/-18 ng/ml, in the extrinsic, intrinsic and intrinsic + thromboplastin psi-serum respectively; values are means+/-SEM) were significantly increased compared with those in the platelet-poor plasma (3 ng/ml). Pentasaccharide, low-molecular-weight heparin and unfractionated heparin inhibited the generation of factor VIIa or its activity, or both, in a dose-dependent manner in all the experimental systems (60-90% inhibition). A kinetic study revealed that the inhibition of the generation of FVIIa by pentasaccharide and heparins starts 1 min after triggering either the extrinsic or the intrinsic clotting pathway. The downregulation of FVIIa by heparins was effected mainly by their anti-Xa activity, but also by their inhibitory effect on the generation of prothrombinase. Pentasaccharide, enoxaparin and unfractionated heparin significantly inhibited prothrombin activation in both extrinsic and intrinsic experimental system. Hirudin had no inhibitory effect either on the generation of FVIIa or on prothrombin activation in any experimental system.

Clinical evaluation of new global clotting assay for monitoring of LMWH treatment: pilot study.

Until now, there has been no reliable method for the monitoring low molecular weight heparin (LMWH) therapy. Based on our observations of the coagulant activity of pseudoserum obtained after clotting of recalcified plasma from patients who were treated with LMWH, we were led to develop a new global clotting assay for the monitoring of this treatment. Methods description. After performing Howell time on PPP, samples were incubated for 30 min in 37 degrees C and they were then centrifuged for 10 min 0.2 ml of this pseudoserum is added to 0.2 ml of citrated normal plasma. Pseudoserum triggered coagulation of normal plasma and the time of new clot formation is expressed in seconds. This assay was called ATHU-test (AHEPA Thromb Haem Unit). We tested 21 normal subjects a in order to define the normal mean value and the range of the method. b) We also checked the reproducibility of the method by repeating the ATHU-test 17 times on the same normal plasma. c) We performed in vitro experiments to study its reliability and we added increasing concentrations using given doses of enoxaparine (4, 8, 12, 16 mg/ml) or fraxiparine (1.5, 3.0, 4.5, 6 u aXa/ml) which was added in vitro to normal plasma confirming the proportional linear regression between duration of our test and the amount of LMWH. Finally d) we checked on the therapy response and the LMWH levels in blood for thrombophiliacs. Results. a) NP, n=21, X=138.6+/-41.1, range 75-225 sec which means that values >X+/-3S=261.9 are distinctively pathological. b) The reproducibility of the method is acceptable, CV=9%. c) It is confirmed that in vitro addition of precautionary doses of LMWH (1.5 u aXa/ml) exceeds the coagulation time of ATHU-test up to 300 sec and it follows a distinctively proportional relationship. d) The monitoring of 20 thrombophiliacs for 2 months proved that: i) All their test times were between 4-15 min. The more we approach the value of 15 min the more danger there is of haemorrhage while, on the contrary, the more values approach 4 min the more the danger of rethrombosis increases. We present the ATHU-test, a simple test which has been used for 6 months now by our Unit, in order to control the LMWH therapy for patients with thromboembolic diseases. The ATHU-test's reproducibility and its small range of normal values, the distinct relationship between therapeutic doses and therapeutic clinical results, as well as the in vitro proof of the linear regression between the coagulation time and the containing amount of LMWH, are likely to establish a new method of choice for the monitoring of LMWH therapy.

Utilization of a new index to distinguish heterozygous thalassemic syndromes: comparison of its specificity to five other discriminants.

In 1984, a new index (the Makris index) combining erythrocytic and platelet parameters was described for the discrimination of the heterozygous thalassemic syndromes (beta and alpha). The algorithm is [(MCV/RDW)/(MPV/PDW)] divided by the RBC count in millions and requires for input the MCV, RDW, MPV, PDW, and RBC. The critical value used for separating the heterozygous thalassemic subjects is 1.84, which is the mean value plus 2 SD of our heterozygous subjects (confidence limit 95%). Because this index utilizes a confidence limit that includes 95% of affected persons, all individuals with values smaller than this need further investigation. It should be noted that the specificity of the index can be increased using the mean value of our heterozygous group plus 3 SD (X + 3 SD = 1.30 + 3*0.27 = 2.11, confidence limit 99%). In a series of 1510 "normal" subjects examined, 154 were designated as abnormals. None of the rest had abnormalities of cellular morphology or red cells osmotic resistance. The algorithm is readily incorporated into the software of an automated, whole blood analyzer. Using an expert system, we compared the sensitivity and specificity of the Makris index to five other discriminants (Mentzer, Shine et al., England et al., Green, and Bessman et al.). The Makris index distinguished between heterozygotes and normals without misdiagnosis.

Lupus anticoagulant--antiphospholipid antibodies and thrombophilia. Relation to protein C--protein S--thrombomodulin.

In order to define the behavior of the lupus anticoagulant and/or antiphospholipid antibodies, we investigated the possible association with protein C, protein S and thrombomodulin. In 19 patients with established diagnosis of an autoimmune disease and coexisting lupus anticoagulant protein C (antigen and activity), protein S (total and free), anticardiolipin and antiphosphatidylserine antibodies were estimated. In one case the IgG globulin fraction containing the inhibitor was separated. The activation rate of pure protein C to its activated form using thrombin/thrombomodulin as activator was then measured in the presence or absence of lupus anticoagulant. No overall decrease of protein C or protein S was detected in patients' plasma. Nevertheless, the lupus anticoagulant had a specific effect on the protein C system, inhibiting the catalytic activity of thrombomodulin without causing a functional protein C deficiency. This specific effect upon thrombomodulin can be a main cause, but not necessarily the only one, for the thrombophilic tendency of patients with the lupus anticoagulant.

The ratio MDA/MDAa as a new index of platelet hyperactivity.

Since 1979, malonyldialdehyde (MDA) is considered a sensitive index of platelet hyperactivity. Stimulators of phospholipase A2 are used in the procedure of MDA production in order to obtain the final quantity (MDAa) which corresponds to the total amount of arachidonic acid present; without stimulation the production of MDA is minimal in non-activated platelets (MDA non-activated). Therefore, the more the MDA/MDAa ratio approaches unity, the more activated are the thrombocytes. We utilized for the first time this new index for the investigation of hyperactive platelets, and we studied 56 persons (17 patients with thrombophilic disease as group A, 17 normals as group B and 22 diabetics without ketoacidosis as group C). We proved that the new index (MDA/MDAa) can be used to detect persons with functionally hyperactive platelets because large differences are found between the mean values of normals and the values of patients with established thrombotic disease, at a high confidence limit (means +/- 3 SD covering 99% of the samples). Comparing the sensitivity of this new index with the other three methods used for the detection of hyperactive platelets [ratio of circulating platelet aggregates (CPA), aggregation with ADP, spontaneous aggregation] in groups B and C we found that only the ratio MDA/MDAa was able to reveal that (a) the two groups B and C are not identical (a statistical conclusion after comparison with the other methods) and (b) there were 5 diabetics in group C who had more hyperactive platelets than the others (these patients were not detected by any other method).

[Platelet volume: comparative study of 2 populations of Greek and French origin]. / Le volume plaquettaire: etude comparative de deux populations d'origine grecque et française.

The number and the volume of blood platelets in 306 normal adult persons of Greek origin were studied in Greece and compared with the corresponding values of 50 normal French adults. These controls were blood donors in the blood bank of the hospital "Necker-Enfants Malades" in Paris. In both phases of the study the same methods and techniques were used by one of the authors. The number of platelets of the Greek subjects (X1) was higher compared to those of the control population (X2) and this difference is statistically significant (means 1 = 295,970/microliters +/- 87,120, means 2 = 267,800/microliters +/- 63,700, P less than 0.05). The platelet volume was only slightly elevated in the Greek population compared to the French population, but this difference is not statistically significant (means 1 = 6.99 mu 3 +/- 2.49, means 2 = 6.59 mu 3 +/- 1.78, P less than 0.1). Our findings in the Greek population are different from those observed by Von Behrens (1975) on Mediterranean immigrants in Australia. Our values in the control population are similar to those of Paulus (1974), but differ from Von Behrens' data in North European subjects. Another observation of this study, is that sex and age (excluding youths) seems to have no influence on platelet volume, but platelet count in men is slightly affected by age.

Factor V leiden and prothrombin G20210A mutations, but not methylenetetrahydrofolate reductase C677T, are associated with recurrent miscarriages.

The aim of this study was to investigate the relationship between recurrent miscarriages and factor V Leiden, prothrombin G20210A and C677T methylenetetrahydrofolate reductase (MTHFR) mutations. In this case-control study the prevalence of factor V Leiden, prothrombin G20210A and C677T methylenetetrahydrofolate reductase mutations was determined in a consecutive series of 80 recurrent miscarriage patients and 100 controls. Fifteen of 80 recurrent miscarriage patients and four out of 100 controls carried the factor V Leiden mutation (19 versus 4%, P = 0.003, odds ratio 5.5, 95% confidence interval (CI): 1.7-17). Seven of 80 recurrent miscarriage patients and two of 100 controls were carriers of the prothrombin G20210A mutation (9 versus 2%, P = 0.038, odds ratio 4.6, 95% CI: 0.9-23.2). Six of 80 recurrent miscarriage women and 15 of 100 controls were homozygotes for the C677T MTHFR mutation (8 versus 15%, P = 0.134, odds ratio: 0.4, 95% CI: 0.1-1.2). Our results suggest that the presence of factor V Leiden and prothrombin G20210A polymorphism, but not MTHFR C677T homozygosity, could be additional risk factors for recurrent miscarriages. Furthermore, it was suggested that the prevalence of factor V Leiden and prothrombin G20210A mutations is more prominent in second trimester, primary fetal losses and it is independent of the existence of additional pathology predisposing to recurrent fetal losses.