Postpartum haemorrhage related early increase in D-dimers is inhibited by tranexamic acid: haemostasis parameters of a randomized controlled open labelled trial.

BACKGROUND: Beneficial effects of tranexamic acid (TA) have been established in surgery and trauma. In ongoing postpartum haemorrhage (PPH), a moderate reduction of blood loss was observed in a previously published randomized controlled trial. Analysis of haemostasis parameters obtained from samples collected as part of this study are presented. METHODS: Women with PPH >800 ml after vaginal delivery were assigned to receive either TA (4 g over 1 h, then 1 g per h over six h) (TA) or not (H). A non-haemorrhagic group (NH), <800 ml blood loss, was included as postpartum reference. At four time-points (enrolment, +30 min, +2 h, +6 h), haemostasis was assessed. Haemostasis assays were performed blinded to group allocation. Data were expressed as median [interquartiles] and compared with non-parametric tests. RESULTS: In H compared with NH group, D-dimers increase (3730 ng ml(-1) [2468-8493] vs 2649 [2667-4375]; P=0.0001) and fibrinogen and factor II decrease were observed at enrolment and became maximal 2 h later. When comparing TA to H patients, the increase in Plasmin-Antiplasmin-complexes at +30 min (486 ng ml(-1) [340-1116] vs 674 [548-1640]; P=0.03) and D-dimers at +2 h (3888 ng ml(-1) [2688-6172] vs 7495 [4400-15772]; P=0.0001) was blunted. TA had no effect on fibrinogen decrease. CONCLUSIONS: This study provides biological evidence of an early increase in D-dimers and plasmin-antiplasmin complexes associated with active post-partum haemorrhage and its attenuation by the early use of a clinically effective high dose of TA, opening the perspective of dose ranging studies to determinate the optimal dose and timing in this setting. CLINICAL TRIAL REGISTRATION: ISRCTN09968140.

Antibodies to macromolecular platelet factor 4-heparin complexes in heparin-induced thrombocytopenia: a study of 44 cases.

As heparin-PF4 (H-PF4) complexes are the target for antibodies associated to heparin-induced thrombocytopenia (HIT), an ELISA has been developed and optimised for testing antibodies binding to H-PF4. This test was consistently negative in 50 healthy subjects (A492 < 0.3) and 35 patients with other causes of thrombocytopenia (A492 < 0.5). In contrast, 43 out of 44 HIT patients showed antibodies to H-PF4 (A492 = 1.70 +/- 0.81) including 5 patients with a negative platelet aggregation test. In one patient with HIT, antibodies to H-PF4 were already present at day 7, whereas platelet counts dropped < or = 100 x 10(9)/l only at days 11-12. Surprisingly, among 41 patients under heparin for > 7 days, 5 showed antibodies to H-PF4, without HIT. These findings underline the major interest of this ELISA for the early diagnosis of HIT. We also showed that LMWH as well as other sulphated polysaccharides can bind to HIT antibodies in the presence of PF4 and that their reactivity is dependent on the molecular weight and the sulphation grade. The mechanism for HIT involves platelet PF4 receptors which bind the macromolecular H-PF4 complexes formed in the presence of a well defined heparin/PF4 ratio.

Clinical applications of a direct assay of free protein S antigen using monoclonal antibodies. A study of 59 cases.

A new one-step ELISA using two monoclonal antibodies specific for distinct epitopes of the free form of protein S (ELISA-m) has been developed for the direct measurement of free protein S in untreated plasma. This assay has been compared with the classic method using polyclonal antibodies to protein S (ELISA-p). The latter method has the drawback of requiring PEG precipitation of plasma which is time-consuming, difficult to perform with accuracy and therefore poorly reproducible in most laboratories. Results of both ELISAs were compared with those of a functional assay. In 30 normal subjects, there was an excellent correlation between ELISA-m and ELISA-p (r = 0.95) as well as between ELISA-m and the functional assay (r = 0.96). In twelve patients with a congenital deficiency, the levels of free protein S antigen were similarly decreased with ELISA-m and ELISA-p and in good agreement with those of protein S activity. In 20 patients with miscellaneous inflammatory diseases, the levels of free proteins S were normal with good correlation between both ELISAs and PS activity, despite high levels of C4bBP-protein S complexes. As expected, in 15 dicoumarol-treated patients, there was a significant and parallel decrease of free protein S antigen with both ELISAs, with even lower levels of protein S activity. In 14 patients with liver cirrhosis, the mean values for free protein S antigen were normal using both assays, but with wide extreme values, whereas protein S activity was significantly lower.(ABSTRACT TRUNCATED AT 250 WORDS)

New direct assay of free protein S antigen using two distinct monoclonal antibodies specific for the free form.

Monoclonal antibodies (mAbs) specific for free protein S and devoid of reactivity with protein S-C4b-BP complexes, have been produced. A one-step sandwich-type enzyme-linked immunoassay (ELISA) has been developed with two mAbs reacting with distinct epitopes of free protein S. F(ab')2 fragments from mAb 15C4 were coated on microplates and mAb 34G2 conjugated with horseradish peroxidase (HRP) was added immediately before diluted plasma. The presence of calcium in the sample diluent prevented dissociation of complexes during the assay. This assay was specific as demonstrated by good recovery of purified protein S added to plasma and the lack of influence of C4B-BP-protein S complexes. Thus, addition of increasing amounts of purified C4B-BP to human citrated plasma induced a dose-dependent decrease of free protein S. The assay was sensitive, allowing measurement of 5-500 ng/ml of free protein S, with a detection threshold of 2 ng/ml. It was also reproducible with inter-assay and intra-assay variation coefficients of 2.5-5.1% and 3.1-5.0%, respectively. Thus, this new ELISA of free protein S antigen in plasma has the advantages of being fast, accurate and reproducible. It appears to be extremely useful for routine studies as no preliminary treatment of plasma is required.

Prevalence of antiphospholipid-related antibodies in unselected patients with history of venous thrombosis.

Antiphospholipid antibodies (aPL) are heterogeneous and are now accepted to be mainly phospholipid-protein-dependent antibodies. Although these antibodies are classically associated with thrombosis, their clinical relevance remains to be established. The subgroups of antibodies characterized by their proteic targets were reported to be more appropriate thrombotic markers. We analysed the prevalence of a large panel of antiphospholipid-related antibodies (aPLR), comprising antibodies directed to phospholipid-protein complexes and to different protein cofactors (beta2GPI, prothrombin, annexin V and protein S), in 122 consecutive unselected patients who had experienced at least one venous thrombotic event. The presence of lupus anticoagulants was assessed with an integrated assay using hexagonal phase phospholipids. Two types of aPL (APA and anti-beta2GPI-PL) were measured using a mixture of phospholipids containing cardiolipin and goat serum or human beta2GPI, respectively, as a source of protein cofactor. Our results show a similar prevalence, close to 15%, of lupus anticoagulants, APA and anti-beta2GPI-PL. In contrast, antibodies to beta2GPI were detected in only 8% of the patients, and very few patients had antibodies directed to other proteins. Of the 35 patients having at least one positive aPLR, 17 were classified as severe, because they had recurrent or early onset of thrombosis (< 35 years). The distribution of aPLR between severe and mild cases was not significantly different except for lupus anticoagulants. Our results clearly indicate that lupus anticoagulant is the only aPLR test to be strongly associated with the severity of thrombosis.

[Organization of urgent blood transfusion in France: analysis of practice patterns in centers involved in care delivery to multiple trauma patients]. / Etat des lieux sur l'organisation de la transfusion sanguine en urgence au sein des établissements de santé français participant à la prise en charge initiale des polytraumatisés.

OBJECTIVE: To describe the organization of medical and transfusion services within the framework of hospital admission for multiple trauma. STUDY DESIGN: National survey in France. MATERIAL AND METHODS: All French hospitals caring for multiple trauma patients were sent a questionnaire. Organization of the medical and transfusion services, and their related resources were evaluated. RESULTS: Among 372 questionnaires sent, 116 replies were received from structures which care for 18 (1-500) multiple trauma patients each year. An orthopaedic and an abdominal surgery unit were widely available whereas a neurosurgeon was available in 21% of responding centers. A transfusion site was found in 43%, whereas others have either a deposit for distribution to specific patients (40%) or a small deposit to cover urgent situations (17%). Comparison with legal or expert based rules of adequate transfusion process disclosed a variable incidence of practice dysfunctions (2-49%) depending on the parameter assessed. CONCLUSION: The French organization of multiple trauma patients' care and blood transfusion delivered for these patients is not homogenous. Dysfunctions were found in all types of hospitals. Recommendations describing good practice seem necessary to be built at the national level.

Megakaryocytes and platelets in myeloproliferative disorders.

Increased megakaryocyte (MK) proliferation in bone marrow is a feature common to the three Ph-negative myeloproliferative disorders (MPDs), i.e. essential thrombocythaemia (ET), polycythaemia vera (PV), and myelofibrosis with splenic myeloid metaplasia (MMM), and to chronic myelocytic leukaemia (CML). Enlarged MKs with multilobulated nuclei and cell clustering in close proximity are the hallmark of all the Ph negative MPDs. Clonality of haematopoietic cells, based on X chromosome inactivation, can now be studied in a majority of female patients in all nucleated cell fractions as well as in platelets. Cytofluorometric studies have demonstrated a shift towards higher ploidy classes in PV and ET MKs which may be useful in discriminating between both primary and reactive thrombocytosis and CML patients which show a significant shift to lower MK ploidy values. The role of MK proliferation on the evolution of myelofibrosis common to MPDs has been firmly established. Implication of platelet-derived growth factor (PDGF) in myelofibrosis has already been demonstrated. More recently transforming growth factor beta (TGF beta) synthesized and secreted by MK has been implicated in fibroblasts stimulation. A significant increase in circulating colony-forming units of MKs (CFU-MK) has been repeatedly observed in MPDs as well as a spontaneous MK colony formation in a majority of ET patients. Hypersensitivity to thrombopoietin (TPO) in relation to a functional defect of the TPO-MPL pathway may play a major role in spontaneous MK growth. There is no currently available test of platelet functions able to predict the risk of occurrence of thrombotic or haemorrhagic complications in MPD patients. However, the role of platelet activation in the pathogenesis of ischaemic erythromelalgia has been established and a correlation between presenting haemorrhagic manifestations and platelet counts in excess of 1000 x 10(9)/l has been found.

[Dysmegakaryocytopoiesis and dysthrombopoiesis in myeloproliferative syndromes]. / Dysmégacaryocytopoïèse et dysthrombopoïése dans les syndromes myéloprolifératifs.

Megakaryocyte proliferation in bone marrow is a feature common to the three Philadelphia negative chromosome myeloproliferative disorders (MPD)--essential thrombocythemia (ET), polycythemia vera, and myelofibrosis with splenic myeloid metaplasia--and chronic myelocytic leukemia. Enlarged megakaryocytes, clustering in close neighbouring with multilobulated nuclei are the hallmark of all the Philadelphia negative chromosome MPD. Clonality of hematopoietic cells, based on X-chromosome inactivation can now be studied in a majority of female patients in all nucleated cell fractions as well as in platelets. A significant increase in circulating CFU-MK has been repeatedly observed in MPD as well as a spontaneous megakaryocyte colony formation in a majority of ET patients. Hypersensitivity to thrombopoietin (TPO) in relation with a functional defect of the TPO-MPL pathway may play a major role in spontaneous megakaryocyte growth. There is presently no currently available test of platelet functions able to predict the risk of occurrence of thrombotic or haemorrhagic complications in MPD patients. However the role of platelets activation in the pathogenesis of ischemic erythromelalgia has been established.

Evidence that a secondary binding and protecting site for factor VIII on von Willebrand factor is highly unlikely.

A binding domain for Factor VIII (F.VIII) has been previously identified on the N-terminal portion of human von Willebrand Factor (vWF) subunit [amino acids (AA) 1-272]. In order to characterize other possible structures of vWF involved in its capacity to bind and to protect F.VIII against human activated protein C (APC), we used a series of purified vWF fragments overlapping the whole sequence of the subunit. Among those were fragments SpIII (dimer; AA 1-1365), SpII (dimer; AA 1366-2050) and SpI (monomer; AA 911-1365) generated by Staphylococcus aureus V8 proteinase, a P34 species (monomer; AA 1-272) obtained with plasmin, a monomeric 39/34 kDa dispase fragment (AA 480-718) and a tetrameric III-T2 fragment (AA 273-511/674-728) produced from SpIII by trypsin. Three other fragments without precise extremities were located using selected monoclonal antibodies to vWF. Two C-terminal fragments of 270 and 260 kDa, overlapping SpI and SpII, were respectively generated from vWF with trypsin and protease 1 from Crotalus atrox venom. An N-terminal 120 kDa fragment, overlapping P34 and 39/34 kDa fragments, was produced by protease 1. Our results show that vWF bound to F.VIII and protected it from degradation by APC in a dose-dependent way. Among the C-terminal and central vWF fragments (SpII, tryptic 270 kDa, 260 kDa, SpI, 39/34 kDa and III-T2), none had the capacity to bind or to protect F.VIII, even at high concentrations. The three N-terminal fragments (SpIII, 120 kDa and P34) bound to F.VIII in a dose-dependent and saturable fashion. SpIII and the 120 kDa fragment had the capacity to protect F.VIII in a dose-dependent way. In contrast, the P34 species did not significantly protect F.VIII, even when using high concentrations of the fragment. In conclusion, the N-terminal end of vWF subunit (AA 1-272) plays a crucial role in binding to F.VIII, but requires additional structures of the 120 kDa fragment to protect it against APC. In addition, the presence of a secondary binding and/or protecting domain on other portions of the vWF subunit (potentially destroyed during the proteolysis of vWF) is highly unlikely.

Generation of antibodies to heparin-PF4 complexes without thrombocytopenia in patients treated with unfractionated or low-molecular-weight heparin.

The incidence of antibodies to heparin-PF4 complexes (H-PF4) has been evaluated in patients who were under heparin therapy for more than 7 days: 109 patients treated with unfractionated heparin (UH) and 100 patients with low-molecular-weight heparin (LMWH). The presence of antibodies was identified in 17% of the former group and 8% of the latter. In both the UH and the LMWH groups, IgM antibodies were found in all but four patients who showed IgA antibodies. IgG isotypes were only detected in five patients and were consistently associated to either IgM or IgA antibodies. The follow-up of H-PF4 antibodies in 76 patients treated with UH from 1 to > or = 12 days showed a relationship between the incidence of antibodies and the duration of therapy. Despite the presence of anti-H-PF4 antibodies there was no thrombocytopenia (<150 10(9)/L) in the patients. A significant drop of platelets requiring the discontinuation of heparin was observed, however, in three patients, but their platelet count consistently remained >150 10(9)/L. Our study demonstrates that the induction of antibodies to H-PF4 is a frequent phenomenon in patients treated with UH or with LMWH. The absence of thrombocytopenia and of clinical complications in these patients demonstrates that other conditions must be associated with H-PF4 antibodies for inducing type II HIT: optimal concentrations of heparin and PF4 in the blood circulation to allow the formation of macromolecular H-PF4 complexes, presence of activated platelets that present an increased binding of H-PF4 complexes, increased expression of FcgammaRIIA receptors, or presence of their H 131 phenotype. We conclude that the measurement of antibodies to H-PF4 complexes allows the detection of heparin-treated patients at risk of developing type II HIT.