Supporting the use of a coagulometric method for rivaroxaban control: a hypothesis-generating study to define the safety cut-offs.

AIMS: Although quantitative anti-FXa assays can be used to measure rivaroxaban plasma levels, they are not widely performed or available. We aimed to tentatively determine the cut-off for thromboembolism and bleeding prevention based on the clotting effect of non-rivaroxaban conjugate-activated FX plasma levels in patients with rivaroxaban using a coagulometric method. METHODS AND RESULTS: Rivaroxaban was added in vitro to normal plasma at a range of 0 to 241 µg/L to cover expected peak and trough levels. Rivaroxaban chromogenic (µg/L) and RVV-confirm as a ratio were determined. Patient plasma samples were assayed with the RVV-confirm reagent. The appropriate rivaroxaban plasma concentration to inhibit clotting mechanisms was based on the remaining FXa in plasma, which was expressed as the ratio of patients/normal, R-C. There is a high correlation between R-C in vitro and spiked normal plasma rivaroxaban concentration (R-Square 0.910, linear equation; 0.971 quadratic equation, p < 0.0001 for both) but not with plasma rivaroxaban chromogenic assays. We propose a cut-off R-C value of 1.65 and 4.5 for safety. Based on the proposed therapeutic range, in 158 assays performed in 58 patients, 6.3 % assays were above the level of bleeding tendency at the peak (R-C 5.39 ± 1.01, median 5.13) and 42 % assays were below the prevention cut-off at the trough (R-C 1.31 ± 0.18, median 1.35). CONCLUSIONS: RVVconfirm® is fast and sensitive to measure the effect of rivaroxaban. Clinical studies are needed to establish whether this cut-off is useful for identifying patients at increased risk of hemorrhage or those who exhibit a low level of anticoagulation.

New oral anticoagulants: are coagulation units still required?

Chronic antithrombotic therapy involves the use of anticoagulants, antiplatelets given either as monotherapy or in combination for the prevention of thrombotic complications. The most feared and sometimes fatal complication with this therapy is bleeding. It should be considered a "golden rule" that a drug or combination of drugs that maximizes efficiency (decreased thromboembolic risk) will probably be less safe (increased risk of bleeding), and this holds true either for single therapy or during combined therapy. The chances of bleeding indicated by risk tables can be useful but show only a snapshot, and the biological, social, environmental, and drug changes and therapeutic adherence also determine changes in the risk of thrombosis and bleeding. Bleeding is an eventuality that occurs in places of "locus minoris resistentiae," and the results of careful phase 3 studies thus cannot be completely predictive of outcomes when a medication is introduced on the pharmaceutical market. With the use of warfarin, the International Normalized Ratio (INR) that has been established to indicate adequately balanced therapy is between 2.0 and 3.0. With the new oral anticoagulants, the pharmaceutical companies emphasize that it is not necessary to monitor anticoagulant effects. In studies with different doses of new oral anticoagulants, however, incidence of clinically significant bleeding complications have been directly related to the doses. Therefore, therapeutic excesses can condition bleeding risk and therapeutic limitation can increase thrombotic risk, especially when short-acting drugs such as the new oral anticoagulants are used. Hence, it is imperative to establish an appropriate method for monitoring new oral anticoagulants, setting levels of safety and effectiveness through periodic dosage and monitoring of their anticoagulant effects. Therefore, we still recommend the use of anticoagulation units for monitoring during treatment with the new oral anticoagulants.

Simple and rapid assay for effect of the new oral anticoagulant (NOAC) rivaroxaban: preliminary results support further tests with all NOACs.

BACKGROUND: New oral anticoagulant (NOAC) drugs are known to influence the results of some routine hemostasis tests. Further data are needed to enable routine assessment of the effects of NOAC on clotting parameters in some special circumstances. METHODS: Following administration of rivaroxaban to patients, at the likely peak and trough activity times, we assessed the effects on prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), and clotting time using Russell's viper venom, and in the presence of phospholipids and calcium reagent available as DVVreagent® and DVVconfirm®. The data were used to determine an adequate NOAC plasma level based on anticoagulant activities expressed as a ratio (patients/normal, R-C). RESULTS: DVVconfirm as R-C could be rapidly performed, and the results were reasonably sensitive for rivaroxaban and probably for other FX inhibitors. This assay is not influenced by lupus anticoagulant and heparin, does not require purified NOAC as control, and will measure whole-plasma clotting activity. CONCLUSIONS: We propose a cut-off R-C value of 4.52 ± 0.33 for safety, but clinical studies are needed to establish whether this cut-off is useful for identifying patients at increased risk of hemorrhage or exhibiting low anticoagulation effect. It also seems possible that normal R-C could indicate an absence of anticoagulant activity when rivaroxaban is discontinued due to episodes of uncontrolled bleeding during anticoagulation or for emergency surgery.

Bleeding tendency in dual antiplatelet therapy with aspirin/clopidogrel: rescue of the template bleeding time in a single-center prospective study.

BACKGROUND: Patients with heightened platelet reactivity in response to antiplatelet agents are at an increased risk of recurrent ischemic events. However, there is a lack of diagnostic criteria for increased response to combined aspirin/clopidogrel therapy. The challenge is to identify patients at risk of bleeding. This study sought to characterize bleeding tendency in patients treated with aspirin and clopidogrel. PATIENTS/METHODS: In a single-center prospective study, 100 patients under long-term aspirin/clopidogrel treatment, the effect of therapy was assayed by template bleeding time (BT) and the inhibition of platelet aggregation (IPA) by light transmission aggregometry (LTA). Arachidonic acid (0.625 mmol/L) and adenosine diphosphate (ADP; 2, 4, and 8 µmol/L) were used as platelet agonists. RESULTS: Bleeding episodes (28 nuisance, 2 hematuria [1 severe], 1 severe proctorrhagia, 1 severe epistaxis) were significantly more frequent in patients with longer BT. Template BT ≥ 24 min was associated with bleeding episodes (28 of 32). Risk of bleeding increased 17.4% for each 1 min increase in BT. Correlation was found between BT and IPAmax in response to ADP 2 µmol/L but not to ADP 4 or 8 µmol/L. CONCLUSION: In patients treated with dual aspirin/clopidogrel therapy, nuisance and internal bleeding were significantly associated with template BT and with IPAmax in response to ADP 2 µmol/L but not in response to ADP 4 µmol/L or 8 µmol/L.

Battle of oral anticoagulants in the field of atrial fibrillation scrutinized from a clinical practice (the real world) perspective.

Warfarin has a long history of benefit and has become the gold standard medication for the prevention of ischemic stroke in patients with atrial fibrillation. Nevertheless, it is far from perfect and there is no doubt that new drugs must be found to replace warfarin. The new oral anticoagulants that are on the market or awaiting approval or under research offer some benefits but not enough to replace warfarin until results of additional studies can show an adequate balance between effectiveness/safety and cost/benefit. There are several issues concerning the new oral anticoagulants. It is essential that the effect of any anticoagulant can be measured in plasma. But to date, there is no test to assess the effect or therapeutic range for the new oral anticoagulants. There is no antidote to neutralize the action of the new drugs in cases of bleeding or when acute surgical intervention is necessary. Dabigatran requires dose adjustment in patients with moderate renal impairment and is contraindicated in patients with severe renal failure. Rivaroxaban should be used with caution in patients with severe renal impairment. Apixaban excretion is also partly dependent on renal function, although the impact of renal insufficiency has not yet been determined. How anticoagulant bridging can be done before surgery has not yet been established. In conclusion, although thousands of patients have been treated in phase III studies, additional data are necessary before conclusions can be drawn on the potential for these new anticoagulant drugs to replace warfarin in patients with atrial fibrillation.

Guidelines for prophylaxis and anti-thrombotic treatment for patients with COVID-19. Consensus of the Latin American Cooperative Group on Hemostasis and Thrombosis (CLAHT) / Guía de profilaxia y tratamiento antitrombótico para pacientes con COVID-19. Consenso del Grupo Cooperativo Latinoamericano en Hemostasia y Trombosis (CLAHT)

Coagulopathy and thrombosis associated with coronavirus disease 2019 (COVID-19) represent a major issue in the management of this disease. In the past months, clinical studies have demonstrated that COVID-19 patients present with a particular hypercoagulable state, in which a markedly increased D-dimer concomitant with increased levels of fibrinogen are observed. This hypercoagulable state leads to an increased risk of thrombosis, which seems to be higher among those patients with critical symptoms of COVID-19. The best therapeutic approach to prevent thrombotic events in COVID-19 has not been determined yet and several questions regarding thromboprophylaxis therapy, such as the time to initiate anticoagulation, type of anticoagulant and dose regimen, have emerged among physicians. To address these concerns, several medical societies have published position papers to provide the opinion of thrombosis experts on the management of coagulopathy and thrombosis associated with COVID-19. In line with this, the Latin America Cooperative Group of Hemostasis and Thrombosis (Grupo CLAHT) has constituted a panel of experts in thrombosis and hemostasis to discuss the available data on this topic. The aim of this review is to summarize the current evidence regarding hemostatic impairment and thrombotic risk in COVID-19 and to provide a carefully revised opinion of Latin American experts on the thromboprophylaxis and management of thrombotic events and coagulopathy in patients with suspected COVID-19.

La coagulopatía y la trombosis asociadas a la enfermedad por coronavirus 2019 (COVID-19) representan un problema importante en el manejo de esta enfermedad. Los estudios clínicos de los últimos meses han demostrado que los pacientes con COVID-19 presentan un estado de hipercoagulabilidad particular, en el que se observa un aumento notable del dímero D concomitante con niveles elevados de fibrinógeno. El estado de hipercoagulabilidad conduce a un mayor riesgo de trombosis, que parece ser mayor entre aquellos pacientes con síntomas críticos de COVID-19. El mejor enfoque terapéutico para prevenir los eventos trombóticos en esta nueva enfermedad aún no se ha determinado y han surgido varias preguntas con respecto a la tromboprofilaxia, como el momento adecuado para iniciar la anticoagulación, el tipo de anticoagulante y el régimen de dosis. Para abordar estas preocupaciones, varias sociedades médicas han publicado artículos de posición para brindar la opinión de expertos en trombosis sobre el manejo de la coagulopatía y trombosis asociadas a COVID-19. Grupo Cooperativo Latinoamericano de Hemostasia y Trombosis (Grupo CLAHT) ha convocado a un panel de expertos en trombosis y hemostasia para discutir los datos disponibles sobre este tema. El objetivo de esta revisión es resumir la evidencia actual con respecto al deterioro hemostático y el riesgo trombótico en el COVID-19 y proporcionar una opinión cuidadosamente revisada de los expertos latinoamericanos sobre la tromboprofilaxis y el manejo de eventos trombóticos y coagulopatía en pacientes con sospecha de COVID-19.

The hemostatic profile of recombinant activated factor VII. Can low concentrations stop bleeding in off-label indications?

BACKGROUND: High concentrations of recombinant activated factor VII (rFVIIa) can stop bleeding in hemophilic patients. However the rFVIIa dose needed for stopping haemhorrage in off-label indications is unknown. Since thrombin is the main hemostatic agent, this study investigated the effect of rFVIIa and tissue factor (TF) on thrombin generation (TG) in vitro. METHODS: Lag time (LT), time to peak (TTP), peak TG (PTG), and area under the curve after 35 min (AUCo-35 min) with the calibrated automated thrombography was used to evaluate TG. TG was assayed in platelet-rich plasma (PRP) samples from 29 healthy volunteers under basal conditions and after platelet stimulation with 5.0 mug/ml, 2.6 mug/ml, 0.5 mug/ml, 0.25 mug/ml, and 0.125 mug/ml rFVIIa alone and in normal platelet-poor plasma (PPP) samples from 22 healthy volunteers, rFVIIa in combination with various concentrations of TF (5.0, 2.5, 1.25 and 0.5 pM). RESULTS: In PRP activated by rFVIIa, there was a statistically significant increase in TG compared to basal values. A significant TF dose-dependent shortening of LT and increased PTG and AUCo-->35 min were obtained in PPP. The addition of rFVIIa increased the effect of TF in shorting the LT and increasing the AUCo-->35 min with no effect on PTG but were independent of rFVIIa concentration. CONCLUSION: Low concentrations of rFVIIa were sufficient to form enough thrombin in normal PRP or in PPP when combined with TF, and suggest low concentrations for normalizing hemostasis in off-label indications.

Anithrombotic prevention in vascular disease: bases for a new strategy in antithrombotic therapy.

A tendency toward bleeding often undercuts the beneficial preventive effect of higher doses of a single antithrombotic drug or combined antithrombotic therapy. Although high doses of antithrombotic drugs may be necessary for optimal prevention, such therapy can also elicit more frequent bleeding. Although major bleeding could be a reversible event is likely to lead clinicians to discontinue antithrombotic therapy which in turn could increase the risk of myocardial infarction, stroke, and cardiovascular death. Thus, to prevent thrombotic events without frequent bleeding complications, the preferred approach might be to use anti-inflammatory drugs in addition to the first-line antithrombotic drugs to reduce inflammation and thrombin formation in atheroma. Although some preliminary data have been already published, to confirm the potential benefit of anti-inflammatory drugs in acute coronary syndromes large prospective double-bind randomized trials are necessary.

Thrombin generation by activated factor VII on platelet activated by different agonists. Extending the cell-based model of hemostasis.

BACKGROUND: Platelet activation is crucial in normal hemostasis. Using a clotting system free of external tissue factor, we investigated whether activated Factor VII in combination with platelet agonists increased thrombin generation (TG) in vitro. METHODS AND RESULTS: TG was quantified by time parameters: lag time (LT) and time to peak (TTP), and by amount of TG: peak of TG (PTG) and area under thrombin formation curve after 35 minutes (AUC-->35min) in plasma from 29 healthy volunteers using the calibrated automated thrombography (CAT) technique. TG parameters were measured at basal conditions and after platelet stimulation by sodium arachidonate (AA), ADP, and collagen (Col). In addition, the effects of recombinant activated FVII (rFVIIa) alone or combined with the other platelet agonists on TG parameters were investigated. We found that LT and TTP were significantly decreased (p < 0.05) and PTG and AUC-->35min were significantly increased (p < 0.05) in platelet rich plasma activated with AA, ADP, Col, and rFVIIa compared to non-activated platelet rich plasma from normal subjects (p = 0.01). Furthermore platelet rich plasma activated by the combined effects of rFVIIa plus AA, ADP or Col had significantly reduced LT and TTP and increased AUC-->35min (but not PTG) when compared to platelet rich plasma activated with agonists in the absence of rFVIIa. CONCLUSION: Platelets activated by AA, ADP, Col or rFVIIa triggered TG. This effect was increased by combining rFVIIa with other agonists. Our intrinsic coagulation system produced a burst in TG independent of external tissue factor activity an apparent hemostatic effect with little thrombotic capacity. Thus we suggest a modification in the cell-based model of hemostasis.

Efficacy assessment of meloxicam, a preferential cyclooxygenase-2 inhibitor, in acute coronary syndromes without ST-segment elevation: the Nonsteroidal Anti-Inflammatory Drugs in Unstable Angina Treatment-2 (NUT-2) pilot study.

BACKGROUND: Despite the use of heparin, aspirin, and other antiplatelet agents, acute coronary syndrome patients without ST-segment elevation remain at risk of cardiovascular thrombotic events. Given the role of inflammation in the pathogenesis of arterial thrombosis, we tested the hypothesis that the combination of meloxicam, a preferential COX-2 inhibitor, and heparin and aspirin would be superior to heparin and aspirin alone. METHODS AND RESULTS: In an open-label, randomized, prospective, single-blind pilot study, patients with acute coronary syndromes without ST-segment elevation were randomized to aspirin and heparin treatment (n=60) or aspirin, heparin, and meloxicam (n=60) during coronary care unit stay. Patients then received aspirin or aspirin plus meloxicam for 30 days. During the coronary care unit stay, the primary outcomes variable of recurrent angina, myocardial infarction, or death was significantly lower in the patients receiving meloxicam (15.0% versus 38.3%, P=0.007). The second composite variable (coronary revascularization procedures, myocardial infarction, and death) was also significantly lower in meloxicam-treated patients (10.0% versus 26.7%, P=0.034). At 90 days, the primary end point remained significantly lower in the meloxicam group (21.7% versus 48.3%, P=0.004), as did the secondary end point (13.3% versus 33.3%, P=0.015) and the need for revascularization alone (11.7% versus 30.0%, P=0.025). No adverse complications associated with the meloxicam treatment were observed. CONCLUSIONS: Meloxicam with heparin and aspirin was associated with significant reductions in adverse outcomes in acute coronary syndrome patients without ST-segment elevation. Additional larger trials are required to confirm the findings of this pilot study.

Abciximab does not inhibit the increase of thrombin generation produced in platelet-rich plasma in vitro by sodium arachidonate or tissue factor.

Aspirin and platelet membrane glycoprotein (GP) IIb/IIIa blockers are currently used for acute coronary events, and in percutaneous coronary intervention for preventing further coronary outcomes, because they inhibit platelet function. Aspirin also inhibits thrombin generation (TG) in platelet-rich plasma (PRP) activated by sodium arachidonate (AA). The effect of the platelet membrane GP IIb-IIIa (integrin alpha(IIb)beta(3)) blocker abciximab on thrombin generation was studied in vitro using PRP. Thirty healthy volunteers taking no medication, and 28 volunteers who had taken aspirin (160 mg/day for 3-4 days), were included in the protocol. Control or in vivo aspirinated PRP, stimulated or not by AA or tissue factor (TF), was investigated for the inhibitory effect of abciximab pre-incubated for 3 minutes. AA and TF added in vitro activated non-aspirinated PRP: lag-time (LT) and time to peak (TTP) were significantly shortened. Peak TG (PTG) and endogenous thrombin potential (ETG) were increased by AA but not TF; thus, AA seems to be more efficient than TF for TG in this system. Abciximab added in vitro to non-activated, non-aspirinated PRP had no effect on LT, TTP, or ETP, but caused a decrease in PTG that was not statistically significant. Abciximab (3 or 4 microg/mL) added in vitro to AA or TF-activated, non-aspirinated PRP produced no effect on TG, although in aspirinated platelets both LT and time to peak were prolonged. AA as well as TF added in vitro to PRP or in vivo aspirinated PRP increased TG, although AA seems to be more efficient in our assay system. Abciximab, which affects non-aspirinated, nonactivated PRP weakly, has no effect on AA or TF in activated control PRP or in vivo aspirinated PRP.

Acute coronary disease Athero-Inflammation: Therapeutic approach.

Antithrombotic therapy is the cornerstone of the treatment of acute coronary syndromes, but there is now evidence which indicates that by blocking inflammation, thrombosis and thus, acute coronary events, could be lowered. The concept of athero-inflammation emerges as the meeting point of different morbidities; dyslipemia, diabetes, hypertension, obesity, immunity, infection, hyperhomocyteinemia, smoking, etc. usual named as risk factors. Thus, beside specific drugs, earliest treatment, in the stage of inflammation, using anti-inflammatory drugs, should be considered since in patients with increased risk of acute coronary process are likely to have many point of origen throughout the coronary arteries. There are a body of evidences for supporting the potential of anti-inflammatory therapy to the prevention of inflammation and atherosclerosis. COX-2 inhibition may decrease endothelial inflammation reducing monocytes infiltration improving vascular cells function, plaque stability and probably resulting in a decrease of coronary atherothrombotic events.Trials including large numbers of patients in prospective double-blind randomized studies worthwhile to confirm the efficacy of NSAID, mainly, COX-2 inhibitors, together with aspirin in the prevention of coronary events in patients with acute coronary disease.

No causal association between inflammation and Chlamydia pneumoniae in patients with chronic ischemic arterial disease.

The C-reactive protein, Chlamydia-specific IgG antibody, and fibrinogen were assayed in the serum of 159 patients with arterial disease (the arterial group) and 203 patients with heart valve prostheses (the valvular group) and no demonstrable coronary disease. In the arterial group, the Chlamydia pneumoniae antibody was > or = 1:32 for 67.3% (107/159) of the patients, the C-reactive protein was elevated in 41.5% (66/159), and the fibrinogen was elevated in 27.7% (44/159). In the valvular group, the C. pneumoniae antibody was > or = 1:32 for 59.1% (120/203) of the patients; the C-reactive protein was elevated in 34.0% (69/203), and the fibrinogen was elevated in 17.2% (35/203). Of 107 patients in the arterial group with C. pneumoniae titers > or = 1:32, only 26 (24.3%) had elevated fibrinogen (426 +/- 29 mg/dL) and 44 (41.1%) had elevated C-reactive protein (1.06 +/- 0.52 mg/dL). Similarly, of the 120 patients in the valvular group with C. pneumoniae titers > or = 1:32, 17 (14.2%) had elevated fibrinogen (409 +/- 29 mg/dL) and 34 had elevated C-reactive protein (0.99 +/- 1.1 mg/dL). Correlated poorly was C. pneumoniae with C-reactive protein and fibrinogen levels. Only the fibrinogen level could be discriminated between the arterial and the valvular group. These results suggest that no causal association exists between inflammation and C. pneumoniae. A highly significant correlation between C-reactive protein and fibrinogen levels was found.

Facilitated thrombolysis: dethrombosis?

Intracoronary thrombus formation results from the combined effects of platelet aggregation and fibrin formation. Fibrinogen plays a significant role in each of these components. Dethrombosis is a therapeutic approach that allows dissolution of a recent thrombus while avoiding the potent fibrinolytic therapies. The less aggressive strategies suggested to achieve dethrombosis are antifibrin, antiplatelet, and defibrinogenation. Glycoprotein receptor antagonists have been beneficial in patients undergoing percutaneous transluminal coronary angioplasty; however, little is known about their potency of inducing reperfusion in acute myocardial infarction. Early use of the strategies suggested to induce dethrombosis (antifibrin, antiplatelet, and defibrinogenation) may facilitate fibrinolysis and primary angioplasty and further induce reperfusion. Nevertheless, the theoretical arguments of facilitated thrombolysis (dethrombosis) have not yet been fruitful as a major clinical benefit except in patients undergoing primary percutaneous coronary intervention.

[Role of anti-inflammatory drugs in the treatment of acute coronary syndromes. From athero-inflammation to athero-thrombosis]. / Papel de los antiinflamatorios en el tratamiento de los síndromes coronarios agudos. De la aterinflamación a la aterotrombosis.

Coronary thrombosis is the most important cause of morbidity and mortality and the most severe manifestation of atherosclerosis. Knowledge of the pathophysiology of atheroma formation and the causes of atheroma accidents have allowed the development of new therapeutic measures for reducing thrombotic events after a coronary episode. Treating the thrombosis after plaque rupture is useful, but a late measure once coronary flow is disturbed. Therefore, treatment at an earlier stage, which we call athero-inflammation, a central event in atheroma progression leading to atherothrombosis, seems wise. There is evidence of an inflammatory component in the pathogenesis of atheroma rupture in acute coronary events. Earlier studies of anti-inflammatory medication have not demonstrated a reduction in thrombotic complications after an acute coronary episode. However, there are pathophysiological arguments and clinical findings that suggest that it would be advisable to include anti-inflammatory medications, especially those that inhibit preferentially COX-2, in the therapeutic arsenal for this pathology. We postulated that blocking athero-inflammation could prevent thrombosis. A pilot study was carried out in 120 patients with acute coronary syndrome without ST-segment elevation in which 60 patients were treated with meloxicam, a preferential COX-2 inhibitor. All patients received heparin and aspirin. During the stay in the coronary care unit, as well as after 90 days, meloxicam lowered composite outcomes (myocardial infarction, death and revascularization procedures) compared with the control group. These results and available pathophysiological and clinical evidence support the hypothesis of potential benefits of non-steroidal anti-inflammatory drugs with preferential inhibitory activity on COX-2 in patients with acute coronary syndromes. More trials are needed to confirm their preventive effect.

Fibrinogen: intra-individual variability in patients with arterial disease and in patients with cardiac valve replacements.

BACKGROUND: Elevated fibrinogen, considered an independent risk factor for coronary disease, stratifies an individual as high risk for coronary disease. A risk marker requires little intra-individual variability during a long period. OBJECTIVES: To establish intra-individual variability of fibrinogen levels in patients with coronary disease. METHODS: We investigated fibrinogen levels prospectively in four blood samples drawn from 267 patients with a history of arterial disease (arterial group) and from 264 patients with cardiac valve replacements (valvular group). The samples were taken during the course of 78.7 and 78.8 days from the arterial and valvular groups respectively. RESULTS: Marked intra-individual dispersion with a reliability coefficient of 0.541 was found in the arterial group and 0.547 in the valvular group. The Bland-Altman test showed low probability to obtain similar results in different samples from the same individual. These results show large intra-individual variability, with similarities in the arterial as well as in the valvular group. CONCLUSIONS: It is not possible to stratify a patient by a specific fibrinogen dosage.