Longitudinal assessment of coagulation potential before, during, and following an in vitro fertilization cycle.

INTRODUCTION: The association between estrogen and hypercoagulability is well-established but little is known about coagulation dynamics during IVF. Our goal was to measure coagulation potential prior to, during, and following an IVF cycle and to investigate differences by conception outcome. MATERIALS AND METHODS: Patients undergoing IVF with fresh embryo transfer at a single academic center using oral contraceptive pills for cycle batching underwent evaluation of thrombin generation using the calibrated automated thrombogram at multiple points during the IVF cycle. Multiple thrombin generation parameters were compared across timepoints and by IVF cycle outcome using ANOVA repeated measures analysis. RESULTS: Of the 17 patients included, 11 conceived. There was a significant increase in peak and total thrombin generation in the entire cohort between the pre-treatment natural follicular phase and following a short course of oral contraceptive pills used for cycle batching. Further increase in these parameters was seen at the time of oocyte retrieval. In the pre-treatment natural follicular phase, patients who conceived had lower peak thrombin generation. There were changes throughout the cycle for factors II, V, VIII, X, XI, XII, antithrombin, and tissue factor pathway inhibitor. Only Factor XI was distinguishable by conception status; values were lower at all visits in patients who conceived. CONCLUSION: Increases in coagulation potential are seen in patients undergoing IVF following a short course of oral contraceptive pills for cycle batching and continue during controlled ovarian hyperstimulation. Those who conceived were seen to have lower peak thrombin generation in the pre-treatment natural follicular phase.

Thrombin Generation Assay in Antiphospholipid Antibodies Positive Subjects as a Personalized Thrombotic Risk Assessment: State of the Art and Perspectives.

PURPOSE OF THE REVIEW: Thrombotic risk assessment in antiphospholipid positive (aPL +) subjects is a major challenge, and the study of in vitro thrombin generation (thrombin generation assays (TGA)) could provide useful information. Activated protein C (APC) sensitivity is involved in thrombotic events in antiphospholipid syndrome patients. We summarized methods used to assess APC sensitivity with TGA and evaluated the prognostic role of APC resistance through literature search. RECENT FINDINGS: APC resistance induced by aPL is a complex pathway. Several cross-sectional studies assessed APC sensitivity to understand thrombotic event mechanisms in aPL + subjects. Only one prospective cohort had investigated the prognostic impact of APC resistance in aPL + subjects, with a positive and significant correlation between APC sensitivity and the risk of thrombosis during the follow up (hazard ratio, 6.07 [95% CI, 1.69-21.87]). APC resistance assessed with TGA could be associated with thrombotic events in aPL + subjects.

Assessment of coagulation assays on Roche Cobas t711 analyzer: performance and clinical implications.

OBJECTIVES: We performed an analytical assessment of five coagulation tests [i.e. prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, thrombin time (TT) and D-dimer] on the Roche Cobas t711 analyzer and a comparison study with the methodology in use at our laboratory (i.e. Werfen ACL Top 750 analyzer), expanding the analysis to the clinical implications of Cobas t711 implementation. METHODS: Imprecision studies were performed following the Clinical and Laboratory Standards Institute (CLSI) H57 A:2008 guideline. Linearity of D-dimer and fibrinogen tests was analysed according to the CLSI EP06-A: 2003 recommendations. For method comparison, the results were analyzed using the Bland-Altman plot and Passing-Bablok regression. RESULTS: Imprecision met manufacturer claims for PT, aPTT and TT. D-dimer and fibrinogen tests showed a coefficient of variation (CV)% over manufacturer claims at certain concentration levels. Linearity ranges could not be verified. Comparison study revealed that results are not interchangeable for any test, a lower correlation for aPTT test and lower D-dimer results from Roche Cobas t711. CONCLUSION: The strength of this study relies on the analysis of the clinical implications of reporting Cobas t711 results compared to those obtained with the methodology in use at our laboratory. Different sensibility to factor deficiency, anticoagulant therapy and interferences might explain lower correlation rates obtained for the aPTT test. Different monoclonal antibodies used for D-dimer determination might explain the lower results obtained with the Cobas t711 analyzer. This aspect needs further studies given the relevance of D-dimer test to exclude thrombotic events and reinforces the need of harmonization in the haemostasis laboratory.

Assessment of Platelet Function by Automated Light Transmission Aggregometry.

Light transmission aggregometry (LTA) has long been the historical "gold standard" of platelet function testing and is typically performed in specialized hemostasis laboratories due to its manual and labor intensive process. However, newer automated testing provides a means of standardization and ability to perform the testing in routine laboratories. Here we describe the measurement of platelet aggregation in the CS-Series™ (Sysmex Corporation, Kobe, Japan) and CN-Series™ (Sysmex Corporation, Kobe, Japan) routine blood coagulation analyzers. Differences in the methods for both analyzers are further described. For the CS-5100™ analyzer, the final diluted concentrations of the agonists are prepared by manual pipetting from reconstituted agonist solutions. These prepared dilutions are eight times concentrated with respect to the final working concentration of the agonists and appropriately diluted within the analyzer to achieve the desired concentration of agonists prior to testing. For the CN-6000™ analyzer, the dilutions of agonists and the final working concentrations are automatically prepared by the auto-dilution feature in the analyzer.

Micro-ultrasonic Assessment of Early Stage Clot Formation and Whole Blood Coagulation Using an All-Optical Ultrasound Transducer and Adaptive Signal Processing Algorithm.

Abnormal formation of solid thrombus inside a blood vessel can cause thrombotic morbidity and mortality. This necessitates early stage diagnosis, which requires quantitative assessment with a small volume, for effective therapy with low risk to unwanted development of various diseases. We propose a micro-ultrasonic diagnosis using an all-optical ultrasound-based spectral sensing (AOUSS) technique for sensitive and quantitative characterization of early stage and whole blood coagulation. The AOUSS technique detects and analyzes minute viscoelastic variations of blood at a micro-ultrasonic spot (<100 µm) defined by laser-generated focused ultrasound (LGFU). This utilizes (1) a uniquely designed optical transducer configuration for frequency-spectral matching and wideband operation (6 dB widths: 7-32 MHz and d.c. ∼ 46 MHz, respectively) and (2) an empirical mode decomposition (EMD)-based signal process particularly adapted to nonstationary LGFU signals backscattered from the spot. An EMD-derived spectral analysis enables one to assess viscoelastic variations during the initiation of fibrin formation, which occurs at a very early stage of blood coagulation (1 min) with high sensitivity (frequency transition per storage modulus increment = 8.81 MHz/MPa). Our results exhibit strong agreement with those obtained by conventional rheometry (Pearson's R > 0.95), which are also confirmed by optical microscopy. The micro-ultrasonic and high-sensitivity detection of AOUSS poses a potential clinical significance, serving as a screening modality to diagnose early stage clot formation (e.g., as an indicator for hypercoagulation of blood) and stages of blood-to-clot transition to check a potential risk for development into thrombotic diseases.

A multi-laboratory assessment of lupus anticoagulant assays performed on the ACL TOP 50 family for harmonized testing in a large laboratory network.

INTRODUCTION: Lupus anticoagulant (LA) testing is commonly performed within hemostasis laboratories, and the ACL TOP 50 family of instruments represent a new "single platform" of hemostasis instrumentation. Our aim was to evaluate these instruments and manufacturer reagents or alternatives for utility in LA testing. METHODS: Comparative evaluations of LA testing using newly installed ACL TOPs 550 and 750 as well as comparative assessments with existing "reference," predominantly Stago, instrumentation, and reagents. Evaluations comprised both dilute Russell viper venom time (dRVVT) and activated partial thromboplastin time (APTT)-based assays. Establishment of normal reference ranges (NRR). RESULTS: The HemosIL dRVVT-based assays showed good comparability with the existing Stago reference method (R > 0.9) and could be considered as verified as fit for purpose. A variety of APTT assays was additionally evaluated for LA utility, and we identified from the assessment good utility of a non-Werfen solution in Hyphen BioMed Cephen reagents. NRR were established based on ≥120 normal individual plasma samples. CONCLUSION: This evaluation of LA reagents on ACL TOP 50 Family instruments identified overall acceptable performance of both dRVVT (Werfen solution) and APTT (non-Werfen solution) to enable harmonization of LA testing in our large network.

Minimizing cost associated with management of heparin-induced thrombocytopenia: A cost analysis of various laboratory testing models.

INTRODUCTION: Management of patients with suspected heparin-induced thrombocytopenia (HIT) can lead to significant costs. Reported cost-saving initiatives have focused on minimizing inappropriate testing in low-risk patients and optimizing alternative anticoagulant selection. We sought to further investigate how utilizing various HIT laboratory testing models would impact total cost of testing and alternative anticoagulant use. METHODS: Utilizing a retrospective cohort of adult patients tested for HIT over three years within our institution, we evaluated how utilization of four distinct laboratory models impacted total number of HIT test combinations completed, time to HIT testing finalization, percentage of patients discharged from the hospital prior to HIT testing finalization, total alternative anticoagulant days, and total anticipated major bleed events. Additionally, we calculated cost of laboratory testing and alternative anticoagulant associated with each model. RESULTS: A total of 482 patients were included in our cohort. A laboratory testing model that utilized an in-house platelet factor 4 (PF4)-heparin enzyme-linked immunosorbent assay (ELISA) completed three days weekly, and reflex serotonin release assay (SRA) with a five-day turnaround resulted in the shortest mean time to HIT testing finalization, lowest percentage of patients discharged prior to HIT testing finalization, and lowest total alternative anticoagulant days. CONCLUSIONS: Institutions should evaluate current HIT laboratory testing practices and assess for opportunities for optimization. Testing models utilizing a PF4-heparin antibody ELISA with a reflex SRA for positive results may improve testing metrics and lead to lower utilization of alternative anticoagulants.

Pre-analytical variables in haemostasis: Findings from the United Kingdom National External Quality Assessment scheme for Blood Coagulation (UK NEQAS BC) haemolysis exercise.

INTRODUCTION: Haemolysis is considered one of the major contributors of nonconformities and sample rejection in coagulation testing. MATERIALS AND METHODS: Two lyophilized plasmas were distributed to 800 centres registered for prothrombin time (PT), activated partial thromboplastin time (APTT) and either Clauss fibrinogen or thrombin time (TT) in the UK NEQAS BC programme. The same pool of normal plasma was used to prepare both samples, to one of which red blood cell haemolysate was added to mimic haemolysis at 3 g/L haemoglobin concentration. Participants were asked to complete a questionnaire about their laboratory approach to dealing with haemolysed samples, including strategies used to deal with different levels of haemolysis. RESULTS: Results for tests performed did not show great differences between the two samples. It should be noted that artificially constructed haemolysed samples may not behave in the same way as patient samples (ie, may not be commutable). However, the possibility of carrying out a large multicentre study for detection of haemolysis was demonstrated. Inconsistency in practice was observed with 226/551 (41%) of centres indicated they reject haemolysed samples solely on visual checks, and 163 (30%) using initial visual checks with further sample rejection evaluation by analyser flags. Furthermore, 333 (72%) of centres indicated that the level of haemolysis affects sample rejection decisions, while 132 (28%) stated it did not. CONCLUSION: Variability of responses for dealing with haemolysed samples reflects a lack of clear consistency in the pre-analytical area of sample processing.

Progress curve analysis of microtitre plate plasma clotting assays. Assessment of tissue factor levels.

MTP plasma clotting assays monitor the time course of fibrin formation in re-calcified plasma by absorbance measurements and are increasingly used as alternatives to traditional one-point clot time assays employed in clinical laboratories to detect thrombotic disorders. The parameters derived from these analyses are analogous to thromboelastography viz. time, rate and maximum extent of clot formation. The derived parameters, based on the whole course of the clotting reaction are more robust, informative and quantitative than single-point clot time assays. However, the parameters themselves are usually obtained arbitrarily by crude graphical analysis of subjectively selected points of progress curves. The current work aimed to investigate the sensitivity and reproducibility of an MTP clotting assay and examine its suitability for measuring tissue factor (TF) levels in cell culture medium and patient urine. The results demonstrate that progress curves can be analysed by fitting a logistic equation, derived from a simplified autocatalytic clot formation model. The parameters, maximum amplitude (Fm), rate constant (k), time to half-maximum amplitude (tm) and maximum rate of clot formation (vm), fit a power curve showing limiting effects with increasing TF concentration. Log/log plots of tm and k against TF concentration provide standard curves for assessment of unknowns.

Performance Assessment of a Multifaceted Unfractionated Heparin Dosing Protocol in Adult Patients on Extracorporeal Membrane Oxygenator.

BACKGROUND: The use of extracorporeal membrane oxygenator (ECMO) support devices are associated with complications, including bleeding and thrombosis. Unfractionated heparin (UFH) is the gold standard anticoagulant in ECMO patients. Clinically, UFH is monitored through activated clotting time (ACT), activated partial thromboplastin time (aPTT), and anti-factor Xa assay. It is unknown which assay best predicts anticoagulation effects in adults. OBJECTIVE: To assess the correlation of UFH dosing and monitoring using an established protocol. METHODS: A pilot, prospective cohort, historically controlled study was conducted at a tertiary care hospital. Patients ≥18 years-old who received ECMO on the multifaceted anticoagulation protocol were included and compared with those on the conventional method of anticoagulation. The primary end point was to assess the correlation between UFH dose and different monitoring methods throughout 72 hours using the new protocol guided by ACT and anti-factor Xa assay. RESULTS: In each arm, 20 patients were enrolled. The study revealed that anti-factor Xa assay had the largest number of "strong" correlations 11/20 (55%), followed by both aPTT and aPTT ratio 10/20 (50%), and, finally, ACT 2/20 (10%). Concordance between anti-factor Xa assay and the other monitoring parameters in the prospective arm was generally low: 31% with aPTT ratio, 26% with ACT, and 23% with aPTT. CONCLUSION AND RELEVANCE: The adaption of a multifaceted anticoagulation protocol using anti-factor Xa assay may provide a better prediction of heparin dosing in adults ECMO patients compared with the conventional ACT-based protocol. Further studies are needed to assess the safety and different monitoring modalities.

The Utility of Preoperative Labs in Predicting Postoperative Complications Following Primary Total Hip and Knee Arthroplasty.

BACKGROUND: Preoperative testing costs billions of dollars despite little evidence supporting its utility. The purpose of this study was to determine the relationship between abnormal preoperative laboratory tests and postoperative complications following total joint arthroplasty. METHODS: The NSQIP database was used to identify 45,936 primary total hip arthroplasty (THA) and 76,041 pri-mary total knee arthroplasty (TKA) cases performed between 2006 and 2013. Complications within 30 days of surgery were collected and multivariable regression modeling was performed incorporating all significant laboratory values as well as demographics and preoperative comorbidities. RESULTS: For THA patients, abnormal sodium (p = 0.016, OR = 1.89), white count (p = 0.043, OR = 1.73), and partial thromboplastin time (p = 0.028, OR = 1.43) were significantly associated with complications. For TKA patients, abnormal alkaline phosphatase (p = 0.04, OR = 2.12), creatinine (p = 0.003, OR = 1.56), and INR (p = 0.008, OR = 1.99) were significantly predictive of complications. CONCLUSION: Of the 13 laboratory values, only six were significantly associated with complications. These findings may have implications for risk stratification in the inpatient setting.

Oral Contraceptives and Venous Thromboembolism: Focus on Testing that May Enable Prediction and Assessment of the Risk.

Combined oral contraceptives (COCs) induce several changes in the levels of coagulation factors. The levels of procoagulant factors are often increased, while levels of anticoagulant factors are decreased. Fibrinolysis is also affected, even if the effect seems to be more counterbalanced by opposite regulation of profibrinolytic and antifibrinolytic factors. These effects on hemostasis are more pronounced with third- or fourth-generation COC compared with second-generation COC. Venous thromboembolism (VTE) risk increases when multiple risk factors, including genetic and environmental, are present simultaneously. COC use causes changes in coagulation that modify the prothrombotic state induced by preexisting hemostatic alterations in a supra-additive manner. Therefore, testing appears to be of importance not only before implementing COC but also to monitor any potential thrombogenicity induced by COC therapy. Inherited genetic factors, such as factor V Leiden, G20210A prothrombin mutation, antithrombin, protein C or protein S deficiencies, non-O blood group, as well as CYP2C9*2 and the rs4379368 mutations, have all been identified as genetic predictive risk factors of VTE in women. Nevertheless, the screening of these genetic biomarkers is not capable of assessing the phenotypic expression of the risk. This review will focus on the different options for screening the thrombogenic status in this population. Specific attention will be given to the endogenous thrombin potential-based activated protein C resistance, a test aiming at assessing the thrombogenicity induced by hormonal therapies and inherited or acquired thrombophilia.

The strengths and weaknesses of viscoelastic testing compared to traditional coagulation testing.

Optimized acute bleeding management requires timely and reliable laboratory testing to detect and diagnose coagulopathies and guide transfusion therapy. Conventional coagulation tests (CCT) are inexpensive with minimal labor requirements, but CCTs may have delayed turnaround times. In addition, abnormal CCT values may not reflect in vivo coagulopathies that require treatment and may lead to overtransfusion. The use of viscoelastic testing (VET) has been rapidly expanding and is recommended by several recent bleeding guidelines. This review is intended to compare CCT to VET, review the strengths and weaknesses of both approaches, and evaluate and summarize the clinical studies that compared CCT-based and VET-based transfusion algorithms. Most studies of CCT vs VET transfusion algorithms favor the use of VET in the management of massively bleeding patients due to reductions in blood product utilization, bleeding, costs, and lengths of stay.

Comparison of acetylsalicylic acid and clopidogrel non-responsiveness assessed by light transmittance aggregometry and PFA-100® in patients undergoing neuroendovascular procedures.

Objectives: Dual platelet inhibition is commonly used for prevention of cardiovascular events in patients undergoing neuroendovascular procedures. Non-responsiveness to platelet inhibitors may be associated with adverse outcomes. The aim of this study was to evaluate the reliability of the platelet function analyzer PFA-100® in comparison to light transmittance aggregometry (LTA) for monitoring clopidogrel and acetylsalicylic acid (ASA) non-responsiveness in a cohort of patients treated for intracranial aneurysm or cranial artery stenosis. Methods: Non-responsiveness to clopidogrel and ASA was assessed by LTA using adenosine diphosphate (ADP) and arachidonic acid and by PFA-100® with the ADP/prostaglandin E1 (PGE1) and collagen/epinephrine cartridges, respectively. Results: A total of 203 patients (145 females; median age, 57 years) were analyzed. Agreement between the two tests was poor for clopidogrel non-responsiveness (ƙ=0.19) and not better than chance for ASA non-responsiveness (ƙ=0.01). Clopidogrel non-responsiveness by LTA and PFA-100® was associated with higher von Willebrand factor antigen and activity levels. ADP-induced platelet disaggregation was lower in patients with clopidogrel non-responsiveness as assessed by PFA-100®. Clopidogrel non-responsiveness by LTA was associated with a higher prevalence of diabetes and a higher body mass index (BMI). Adverse outcomes (death, thromboembolism, or in-stent thrombosis) occurred in 13% (n=26) of all patients independently of ASA and clopidogrel non-responsiveness as assessed by both devices. Conclusions: Our results show that LTA and PFA-100® are not interchangeable in the assessment of ASA and clopidogrel non-responsiveness in patients undergoing neuroendovascular interventions.

Viscoelastic Tests as Point-of-Care Tests in the Assessment and Management of Bleeding and Thrombosis in Liver Disease.

Viscoelastic point-of-care (VET POC) tests provide a global assessment of hemostasis and have an increasing role in the management of bleeding and blood component delivery across several clinical settings. VET POC tests have a rapid turnaround time, provide a better overall picture of hemostasis, predict bleeding more accurately than conventional coagulation tests, and reduce blood component usage and health care costs. Despite commonly having abnormal conventional coagulation tests, most patients with chronic liver disease have a "rebalanced" hemostasis. However, this hemostatic balance is delicate and these patients are predisposed to both bleeding and thromboembolic events. Over recent years, VET POC tests have been increasingly studied for their potential as better functional tests of hemostasis in liver disease patients. This review provides a background on the most common VET POC tests (thromboelastography and rotational thromboelastometry) and discusses the current evidence for these tests in the prediction and management of bleeding and thrombosis in patients with chronic liver disease, and in liver resection and transplant. With the recent publication of several randomized controlled trials, there is growing evidence that VET POC tests may be used to improve bleeding risk assessment and reduce blood product use in liver disease patients outside of the transplant setting. However, consensus is still lacking regarding the VET POC tests' thresholds that should be used to trigger blood product transfusion. VET POC tests also show promise in predicting thrombosis in patients with liver disease, but further research is needed before they can be used to guide anticoagulant therapy.

Laboratory Assessment of Coagulation Factor XIII.

Laboratory diagnosis of congenital and acquired deficiencies of coagulation factor XIII (FXIII) can be challenging. Determination of FXIII function requires specific and sensitive assays which are not always available. This brief review article summarizes currently used FXIII assay methods, their principles and difficulties, and discusses the recommended diagnostic workup in case of a suspected FXIII deficiency. The article also briefly touches on experimental methods used in FXIII research.

Assessment of the reliability and validity of a novel point-of-care fibrinogen (F-Point) device against an industry standard at fibrinogen levels >2 g/L in non-haemorrhage scenarios.

INTRODUCTION: A diagnostic accuracy study assessing the reliability and validity of a novel plasma fibrinogen point-of-care (F-Point) device compared with the von Clauss method of assay. METHODS: Forty-one women presenting for elective caesarean delivery and 43 non-pregnant female patients presenting for elective gynaecological surgery were recruited to assess agreement at normal fibrinogen levels (elective gynaecological cohort) and high fibrinogen levels (elective caesarean section cohort). Validity was assessed by comparing the F-Point results with the gold standard of von Clauss fibrinogen assay performed on the ACL Top 500. Reliability (test-retest) and validity were assessed using the intraclass correlation to control for operator variance (two-way random absolute agreement method), presented as intra class correlation coefficients (ICCs) and 95% confidence interval, and Bland-Altman analysis, presented as mean bias and 95% limits of agreement and coefficient of variation (COV). RESULTS: The results demonstrated a high test-retest reliability demonstrated in the paired F-Point measurements with an intraclass correlation coefficient (ICC) of 0.95, a bias of 0 (-00.69 to 0.69) and a COV of 9%. Similarly, there was acceptable agreement demonstrated between F-Point and von Clauss assay with an ICC of 0.91, a bias of -0.1 (-0.96 to 0.75) and a COV of 11%. CONCLUSIONS: Our novel plasma fibrinogen point-of-care device has been shown to be reliable and valid when testing fibrinogen levels as low as 2 g/L. Future studies investigating the correlation at lower fibrinogen levels, for example during haemorrhage and in patients with coagulopathies, are required.

Seasonal and meteorological associations of vitamin K-dependent coagulation factors in 1-month-old infants: assessment of Normotest values.

: We aimed to determine the presence of seasonal and meteorological associations of the activity of vitamin K-dependent coagulation factors to explain the seasonal variation in vitamin K deficiency-related bleeding. Seasonal and monthly changes in Normotest values in 1759 healthy 1-month-old infants were retrospectively accessed, and the impact of meteorological parameters on Normotest values was analyzed. Normotest values peaked in winter and were the lowest in summer, with statistically significant differences among the seasonal values (P < 0.001). Comparing monthly variations, the values peaked in January and were the lowest in August (P < 0.001). Only the average daily air temperature significantly correlated with the Normotest values on multiple linear regression (P < 0.001) and with low Normotest values on multiple logistic regression analysis (odds ratio, 1.023; P = 0.002). Seasonal and monthly variations in Normotest values were observed in 1-month-old infants, possibly due to fluctuations in daily air temperature.

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.