Use of thromboelastography and thrombin generation assay to predict clinical phenotype in patients with severe FVII deficiency

Clinical, Laboratory, and Molecular Aspects of Factor VII Deficiency

Congenital factor VII (FVII) deficiency, the most frequent among the recessively inherited disorders of blood coagulation, is characterized by a wide range of symptoms, from mild mucosal bleeds to life-threatening intracranial hemorrhage. Complete FVII deficiency may cause perinatal lethality. Clinically relevant thresholds of plasma levels are still uncertain, and modest differences in low FVII levels are associated with large differences in clinical phenotypes. Activated FVII (FVIIa) expresses its physiological protease activity only in a complex with tissue factor (TF), which triggers clotting at a very low concentration. Knowledge of the FVIIa-TF complex helps to interpret the clinical findings associated with low FVII activity as compared with other rare bleeding disorders and permits effective management, including prophylaxis, with recombinant FVIIa, which, however, displays a short half-life. Newly devised substitutive and nonsubstitutive treatments, characterized by extended half-life properties, may further improve the quality of life of patients. Genetic diagnosis has been performed in thousands of patients with FVII deficiency, and among the heterogeneous F7 mutations, mostly missense changes, several recurrent variants show geographical distribution and identity by descent. In the general population, common F7 polymorphisms explain a large proportion of FVII level variance in plasma through FVII-lowering effects. Their combination with pathogenic variants may impact on the frequent detection of FVII coagulant levels lower than normal, as well as on mild bleeding conditions. In the twenties of this century, 70 years after the first report of FVII deficiency, more than 200 studies/reports about FVII/FVII deficiency have been published, with thousands of FVII-deficient patients characterized all over the world.

Viscoelastic testing guided coagulation management in factor VII deficiency for spinal anaesthesia and caesarean section

The risks and benefits of spinal anaesthesia must be assessed in patients with coagulation disorders. A woman in her 20s with congenital factor VII (FVII) deficiency (31%) was admitted at 38 weeks for caesarean delivery. A rotational thromboelastometry (ROTEM) analysis showed normal coagulation and spinal anaesthesia was performed safely. A repeated ROTEM analysis after haemostasis and uterine closure showed normal coagulation without fibrinolysis. No prophylactic FVII was administered, resulting in a cost savings of US$12 884. FVII level did not predict bleeding or fibrinolysis and FVII and tranexamic acid were not indicated.

Perioperative ROTEM® evaluation in a patient affected by severe VII factor deficiency undergoing microvascular decompression craniotomy for hemifacial spasm

The potential use of TEG/ROTEM® in evaluating the bleeding risk for rare coagulation disorders needs to be assessed, considering the common mismatch among laboratory tests and the clinical manifestations. As a result, there is currently no published data on the use of viscoelastic tests to assess coagulation in FVII deficient patients undergoing elective neurosurgery. We describe the case of a patient affected by severe FVII deficiency who underwent microvascular decompression (MVD) craniotomy for hemifacial spasm (HFS). The ROTEM® did not show a significant coagulopathy according to the normal ranges, before and after the preoperative administration of the recombinant activated FVII, but a substantial reduction in EXTEM and FIBTEM Clotting Times was noted. The values of coagulation in standard tests, on the contrary, were indicative of a coagulopathy, which was corrected by the administration of replacement therapy. Whether this difference between ROTEM® and standard tests is due to the inadequacy of thromboelastographic normal ranges in this setting, or to the absence of clinically significant coagulopathy, has yet to be clarified. Neurosurgery is a typical high bleeding risk surgery; additional data is required to clarify the potential role for thromboelastographic tests in the perioperative evaluation of the FVII deficient neurosurgical patients.

The Choice between Plasma-Based Common Coagulation Tests and Cell-Based Viscoelastic Tests in Monitoring Hemostatic Competence: Not an either-or Proposition

There has been a significant interest in the last decade in the use of viscoelastic tests (VETs) to determine the hemostatic competence of bleeding patients. Previously, common coagulation tests (CCTs) such as the prothrombin time (PT) and partial thromboplastin time (PTT) were used to assist in the guidance of blood component and hemostatic adjunctive therapy for these patients. However, the experience of decades of VET use in liver failure with transplantation, cardiac surgery, and trauma has now spread to obstetrical hemorrhage and congenital and acquired coagulopathies. Since CCTs measure only 5 to 10% of the lifespan of a clot, these assays have been found to be of limited use for acute surgical and medical conditions, whereby rapid results are required. However, there are medical indications for the PT/PTT that cannot be supplanted by VETs. Therefore, the choice of whether to use a CCT or a VET to guide blood component therapy or hemostatic adjunctive therapy may often require consideration of both methodologies. In this review, we provide examples of the relative indications for CCTs and VETs in monitoring hemostatic competence of bleeding patients.

Viscoelastic testing in benign hematologic disorders: Clinical perspectives and future implications of point-of-care testing to assess hemostatic competence

Viscoelastic tests (VETs) have been used routinely for liver transplantation, cardiac surgery, and trauma, but only recently have found clinical utility in benign hematologic disorders. Therefore, guidelines for diagnosis and treatment of these disorders based on viscoelastic variables have been adapted from the existing transplant, cardiothoracic surgery, and trauma resuscitation literature. As a result, diagnostic and therapeutic strategies for benign hematologic disorders utilizing VETs are not uniform. Accordingly, even though there has been a recent increase in the utilization of VET for the diagnosis and treatment of such disorders, the literature is still in its early stages. Analysis of point-of-care viscoelastic tracings from benign hematologic disorders has the potential to allow prompt recognition of disease and to guide patient-specific intervention. Here we present a review describing the application of VETs to benign hematologic disorders.

Novel mutation in coagulation factor VII (Carmel mutation): Identification and characterization

BACKGROUND

Measurement of factor VII (FVII) activity does not enable prediction of bleeding tendency in individuals with inherited FVII deficiency.

OBJECTIVE

To characterize the molecular and functional features of FVII in a family with FVII deficiency and correlate them with the bleeding tendency.

PATIENTS/METHODS

We studied 7 family members with very low FVII activity using prothrombin time (PT), activated factor VII (FVIIa), FVII activity level, and thrombin generation. The factor 7 gene was sequenced and the mutation was analyzed by prediction software.

RESULTS

The proband has very low FVII activity (0%-4%), with PT ranging between 5% to 18% depending on the tissue factor (TF) origin. Direct sequencing demonstrated a single homozygous nucleotide substitution G > A in exon 6, predicting a novel missense mutation Cys164Tyr. Three members of the family were found to be heterozygous carriers of this mutation. One of them was a compound heterozygote, carrying both the Cys164Tyr and Ala244Val mutation (linked to Arg353Gln polymorphism). Her FVII activity and antigen levels were 3%-7% and 8%, respectively. The other heterozygous carriers demonstrated FVII activity of 41%-54%, FVII antigen of 46%-66%, and FVIIa activity of 30%. FVIIa was undetectable in the homozygous and compound heterozygous subjects. Thrombin generation was normal in the presence of calcium, but no response to TF addition was observed in the homozygous proband, and a reduced response was observed in the compound heterozygous subject.

CONCLUSION

The patient homozygous for the "Carmel" mutation has mild clinical manifestations despite very low FVII activity, which correlates with thrombin generation results.

Evaluation of Bleeding Phenotype of Inherited Factor VII Deficiency in Children With a Bleeding Assessment Tool and Global Assays

INTRODUCTION

Inherited factor VII (FVII) deficiency is the most common of the rare bleeding disorders and shows a heterogenous distribution of bleeding phenotypes independent of factor activity level. The bleeding score (BS) evaluates the phenotype of patients with rare bleeding disorders. Thromboelastography (TEG) and thrombin generation assays (TGAs) are 2 methods to evaluate global hemostasis, and controversially both tests are useful for identifying different bleeding tendency phenotypes. The purpose of this study was to investigate the use of the BS and global assays (TEG and TGAs) to predict the bleeding phenotype of inherited FVII deficiency.

MATERIALS AND METHODS

A total of 27 patients with FVII deficiency were evaluated with the BS and global hemostasis assays.

RESULTS

The BS was compatible with disease severity according to the FVII activity level (P<0.05) but the BS and bleeding grade of patients did not show a statistically significant correlation with factor activity level (P>0.05). No significant correlation was observed between the factor activity level and any TEG parameter (P>0.05). The factor activity level was negatively correlated with the lag time of the TGA on the contrary positively correlated with the peak thrombin time of the TGA (P<0.05).

CONCLUSIONS

The global assays do not successfully predict the bleeding phenotype. The BS is a more suitable tool than conventional and global assays for predicting the bleeding phenotype.

Benefits of Thromboelastography and Thrombin Generation Assay for Bleeding Prediction in Patients With Thrombocytopenia or Hematologic Malignancies

Background

Thromboelastography (TEG) provides comprehensive information on the whole blood clot formation phases, whereas thrombin generation assay (TGA) reveals the endogenous thrombin levels in plasma. We investigated the potential significance of TEG and TGA parameters for prediction of clinical bleeding in hematologic patients on the basis of the patient's platelet levels.

Methods

TEG and TGA were performed in 126 patients with thrombocytopenia or hematologic malignancies. The bleeding tendencies were stratified on the basis of the World Health Organization bleeding grade.

Results

Maximum amplitude (MA) and clot formation in TEG and endogenous thrombin potential (ETP) in TGA showed significant associations with high bleeding grades (P=0.001 and P=0.011, respectively). In patients with platelet counts ≤10×10⁹/L, low MA values were strongly associated with a high bleeding risk. For bleeding prediction, the area under the curve (AUC) of MA (0.857) and ETP (0.809) in patients with severe thrombocytopenia tended to be higher than that of platelets (0.740) in all patients. Patients with platelet counts ≤10×10⁹/L displayed the highest AUC of the combined MA and ETP (0.929).

Conclusions

Both TEG and TGA were considered to be good predictors of clinical bleeding in patients with severe thrombocytopenia. Combination of the ETP and MA values resulted in a more sensitive bleeding risk prediction in those with severe thrombocytopenia.

F7 gene variants modulate protein levels in a large cohort of patients with factor VII deficiency. Results from a genotype-phenotype study

Congenital factor VII (FVII) deficiency is a rare bleeding disorder caused by mutations in F7 gene with autosomal recessive inheritance. A clinical heterogeneity with poor correlation with FVII:C levels has been described. It was the objective of this study to identify genetic defects and to evaluate their relationships with phenotype in a large cohort of patients with FVII:C<50 %. One hundred twenty-three probands were genotyped for F7 mutations and three polymorphic variants and classified according to recently published clinical scores. Forty out of 123 patients (33 %) were symptomatic (43 bleedings). A severe bleeding tendency was observed only in patients with FVII:C<0.10 %. Epistaxis (11 %) and menorrhagia (32 % of females in fertile age) were the most frequent bleedings. Molecular analysis detected 48 mutations, 20 not reported in the F7 international databases. Most mutations (62 %) were missense, large deletions were 6.2 %. Compound heterozygotes/homozygotes for mutations presented lower FVII:C levels compared to the other classes (Chi2=43.709, p<0,001). The polymorphisms distribution was significantly different among the three F7 genotypic groups (Chi2=72.289, p<0,001). The presence of truncating mutations was associated with lowest FVII:C levels (Chi2=21.351, p=0.002). This study confirms the clinical and molecular variability of the disease and the type of symptoms. It shows a good correlation between the type of F7 mutation and/or polymorphisms and FVII:C levels, without a direct link between FVII:C and bleeding tendency. The results suggest that large deletions are underestimated and that they represent a common mechanism of F7 gene inactivation which should always be investigated in the diagnostic testing for FVII deficiency.

Ischemic stroke in a patient with moderate to severe inherited factor VII deficiency

Thrombosis is known to occur in patients with rare inherited bleeding disorders, usually in the presence of a thrombotic risk factor such as surgery and/or factor replacement therapy, but sometimes spontaneously. We present the case of a 72-year-old African American male diagnosed with congenital factor VII (FVII) deficiency after presenting with ischemic stroke, presumably embolic, in the setting of atherosclerotic carotid artery stenosis. The patient had an international normalized ratio (INR) of 2.0 at presentation, with FVII activity of 6% and normal Extem clotting time in rotational thromboelastometry. He was treated with aspirin (325 mg daily) and clopidogrel (75 mg daily) with no additional bleeding or thrombotic complications throughout his admission. This case provides further evidence that moderate to severe FVII deficiency does not protect against thrombosis.