Functional fibrinogen (FLEV-TEG) versus the Clauss method in an obstetric population: a comparative study

Fibrinogen as a potential diagnostic marker for prediction and evaluation of postpartum hemorrhage: a retrospective study

OBJECTIVE

To investigate whether prenatal fibrinogen (FIB) or other related factors could be utilized to evaluate the risk of postpartum hemorrhage (PPH).

METHODS

A retrospective study was conducted in a database from January 2015 to December 2019. A total of 128 patients were enrolled and evaluated with FIB, in which 55 patients were assigned to low FIB and 73 in normal FIB.

RESULTS

According to the volume of blood loss, the mean of the low FIB group (<4 g/L) was markedly higher than that of the normal FIB group (≥4 g/L). Prenatal FIB was negatively correlated with PPH volume. The receiver operating characteristic (ROC) curve results indicated that the value of prenatal FIB was 0.701 to predict refractory PPH.

CONCLUSIONS

Prenatal FIB was significantly related to thrombin time (TT), which may be an independent factor to predict the coagulation state of prenatal pregnancy.

Thromboelastography versus Standard Coagulation Assays in Patients with Postpartum Hemorrhage

OBJECTIVE

 Thromboelastography (TEG), a point-of-care test that measures blood's dynamic viscoelastic properties, is routinely used to guide resuscitation in surgical specialties with high hemorrhage risk. Patients with ongoing postpartum hemorrhage (PPH) often develop coagulopathy and hypofibrinogenemia. Timely assessment of fibrinogen is crucial because cryoprecipitate for repletion requires thawing time prior to administration. TEG may provide rapid assessment of coagulopathy in ongoing hemorrhage but this has not been thoroughly studied. Our objective was to determine if TEG accurately reflects coagulopathy in ongoing PPH when compared with standard assays.

STUDY DESIGN

 This was a retrospective cohort study of people with ongoing PPH (quantified blood loss >1,000 mL), from January 1, 2016, to December 31, 2019. TEG variables and standard coagulation parameters were compared in patients who had both assays drawn simultaneously. As a secondary analysis, patients who had TEG were compared with those who did not. The Mann-Whitney, Fisher's exact, Kruskal-Wallis, Spearman's rho, and logistic regression tests were used for analysis. Significance was set at p < 0.05.

RESULTS

 A total of 680 patients were included, 69 of whom had TEG and coagulation parameters drawn simultaneously and were included in the primary analysis. The remainder were included in the secondary analysis. TEG variables and coagulation assays correlated significantly-prolonged R with increased PTT (rho 0.25, p = 0.04), prolonged K and decreased α angle with decreased fibrinogen (rho -0.61, p < 0.001; rho 0.24, p < 0.001), and decreased maximum amplitude with decreased platelets (rho 0.62, p < 0.001). Those who had thromboelastographic assays had higher blood loss and need for interventions to manage hemorrhage than those who did not.

CONCLUSION

 TEG correlated significantly with standard laboratory assays in ongoing PPH, including for patients with hypofibrinogenemia. Given the point-of-care nature and rapid turnaround time, TEG should be considered for timely hemorrhage evaluation and directed resuscitation of coagulopathy.

KEY POINTS

· TEG significantly correlates with standard laboratory measures of coagulopathy in postpartum hemorrhage, including in patients with hybofibrinogemia (fibrinogen <200).. · TEG is routinely used in nonobstetric hemorrhage, and should be considered in PPH.. · Due to the point-of-care nature, TEG may allow for rapid guided resuscitation, including fibrinogen..

Hemostasis in Pre-Eclamptic Women and Their Offspring: Current Knowledge and Hemostasis Assessment with Viscoelastic Tests

Pre-eclampsia (PE) is a placenta-mediated disease and remains a major cause of maternal and neonatal mortality and morbidity. As PE develops, normal pregnancy's hypercoagulable balance is disrupted, leading to platelet hyperactivation, excessive pathological hypercoagulability, and perturbed fibrinolysis. This narrative review aims to summarize the current knowledge regarding hemostasis in PE compared with healthy gestation and the potential effects of maternal PE on neonatal hemostasis. Finally, it aims to discuss hemostasis assessments for normal pregnancies and PE, emphasizing the role of viscoelastic tests, namely, thromboelastography (TEG) and thromboelastometry (ROTEM), for monitoring PE-associated hemostatic alterations. The use of TEG/ROTEM for assessing the hemostatic profile of PE women has been little considered, even though conventional coagulation tests (CCTs) have not helped to monitor hemostasis in this population. Compared with normal pregnancy, TEG/ROTEM in PE reveals an excessive hypercoagulability analogous with the severity of the disease, characterized by higher-stability fibrin clots. The TEG/ROTEM parameters can reflect PE severity and may be used for monitoring and as predictive markers for the disease.

Potential for prolongation of fibrinogen concentrates post-reconstitution

BACKGROUND AND OBJECTIVES

Reconstituted fibrinogen concentrate is considered stable for 8-24 h based on product monographs. Given the long half-life of fibrinogen in vivo (3-4 days), we hypothesized that reconstituted sterile fibrinogen protein would remain stable longer than 8-24 h. Extending the expiry date for reconstituted fibrinogen concentrate could decrease wastage and facilitate reconstitution in advance to minimize turnaround times. We performed a pilot study to define the stability of reconstituted fibrinogen concentrates over time.

MATERIALS AND METHODS

Reconstituted Fibryga® (Octapharma AG) from 64 vials was stored in the temperature-controlled refrigerator (4 °C) for up to 7 days with functional fibrinogen concentration measured serially using the automated Clauss method. The samples were frozen, then thawed and diluted with pooled normal plasma in order for them to be batch tested.

RESULTS

Reconstituted fibrinogen samples stored in the refrigerator showed no significant reduction in functional fibrinogen concentration for the entire 7-day study period (p = 0.63). Duration of initial freezing had no detrimental effect on functional fibrinogen levels (p = 0.23).

CONCLUSION

Fibryga® can be stored at 2-8 °C post-reconstitution for up to one week with no loss in functional fibrinogen activity based on Clauss fibrinogen assay. Further studies with other fibrinogen concentrate formulations and clinical in vivo studies may be warranted.

Comparative retrospective study on the validity of point-of-care testing device for massive obstetrical hemorrhage: dry hematology vs thromboelastography

BACKGROUND

Early recognition of hypofibrinogenemia and prompt initiation of transfusion therapy in patients with massive obstetrical hemorrhage can improve prognosis. There are reports on the usefulness of point-of-care testing, which provides quicker test results compared with fibrinogen measurements using the conventional Clauss method.

OBJECTIVE

This study aimed to compare and investigate the diagnostic accuracy of dry hematology and thromboelastography in point-of-care testing for the diagnosis of hypofibrinogenemia.

STUDY DESIGN

A single-center, retrospective study of 126 massive obstetrical hemorrhage cases with point-of-care testing before treatment was initiated. The correlation of fibrinogen values with the Clauss method and the diagnostic accuracy for hypofibrinogenemia were compared between dry hematology and thromboelastography.

RESULTS

Fibrinogen value in dry hematology showed a strong positive correlation with values measured by the Clauss method, and the diagnostic accuracy for hypofibrinogenemia was high, but there were many residuals above 100 mg/dL, and the distribution of these residuals was not uniform. Although thromboelastography cannot be used to directly measure fibrinogen values, maximum amplitude citrated functional fibrinogen, amplitude-10 citrated rapid thromboelastography, and amplitude-10 citrated functional fibrinogen showed a strong positive correlation with fibrinogen values using the Clauss method, and no significant difference in correlation or diagnostic accuracy was observed relative to dry hematology.

CONCLUSION

Dry hematology and thromboelastography were equally accurate in diagnosing hypofibrinogenemia, with results correlating well with fibrinogen values measured by the Clauss method.

Role of Viscoelastic and Conventional Coagulation Tests for Management of Blood Product Replacement in the Bleeding Patient

An important aim of viscoelastic testing (VET) is to implement transfusion algorithms based on coagulation test results to help reduce transfusion rates and improve patient outcomes. Establishing a rapid diagnosis and providing timely treatment of coagulopathy is the cornerstone of management of severely bleeding patients in trauma, postpartum hemorrhage, and major surgery. As the nature of acute bleeding and trauma leads to an unstable and tenuous physiologic state, conventional coagulation tests (CCTs) are too slow to diagnose, manage, and also course correct any hemostatic abnormalities that accompany an acute critical illness. Viscoelastic point-of-care tests strongly correlate with results from standard laboratory tests but are designed to enable clinicians to make timely, informed bleeding management decisions when time to intervene is critical. These assays provide an individualized and goal-oriented approach to patient blood management and are increasingly becoming involved in transfusion algorithms. The scope of this review aims to evaluate the current literature on VETs and their impact on actionable outputs in clinical decision making and their relationship to CCT.

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 haemostatic point-of-care assays in the management of postpartum haemorrhage: a narrative review

Viscoelastic haemostatic assays provide rapid testing at the bed-side that identify all phases of haemostasis, from initial fibrin formation to clot lysis. In obstetric patients, altered haemostasis is common as pregnancy is associated with coagulation changes that may contribute to bleeding events such as postpartum haemorrhage, as well as thrombosis events. In this narrative review, we examine the potential clinical utility of viscoelastic haemostatic assays in postpartum haemorrhage and consider the current recommendations for their use in obstetric patients. We discuss the clinical benefits associated with the use of viscoelastic haemostatic assays due to the provision of (near) real-time readouts with a short turnaround, coupled with the identification of coagulation defects such as hypofibrinogenaemia. The use of viscoelastic haemostatic assay-guided algorithms may be beneficial to diagnose coagulopathy, predict postpartum haemorrhage, reduce transfusion requirements and monitor fibrinolysis in women with obstetric haemorrhage. Further studies are required to assess whether viscoelastic haemostatic assay-guided treatment improves clinical outcomes, and to confirm the utility of prepartum viscoelastic haemostatic assay measurements for identifying patients at risk of postpartum haemorrhage.

Monitoring of hemostatic parameters for early prediction of first-trimester miscarriage

BACKGROUND

Hypercoagulation starts as early as the first-trimester pregnancy and is a risk factor for thromboembolic events which are associated with miscarriage. Our study aimed to investigate coagulation, platelets, and fibrinolysis parameters alteration amongst trimester-specific normal pregnancy and first-trimester miscarriage patients. We also test the accuracy of haemostatic parameters determination for prediction of first-trimester miscarriage.

METHODS

Retrospective investigation of 50 women whose most recent pregnancy had ended in the first trimester and 54 age-matched consecutive normal pregnancy between 2016 and 2019. Furthermore, 51 non-pregnant, age-matched women were included in parallel to healthy controls. Twelve screening tests for coagulation and platelet parameters were assessed.

RESULTS

We found plasma levels of aPTT, FBG, and TT were significantly prolonged or decreased in miscarriage subjects than the corresponding first phase in normal pregnancies. PT, INR, aPTT, and d-dimer all shift back to normal in miscarriage patients compared with non-pregnant women. Shortened aPTT combined with TT and FBG can predicted the occurrence of first-trimester miscarriage with an AUC of 0.831.

CONCLUSIONS

Routine assessment of aPTT combined with TT and FBG is a low-cost, widely available marker for prediction of first-trimester miscarriage.

Pediatric Thromboelastograph 6s and Laboratory Coagulation Reference Values

CONTEXT.—

Specific reference intervals (RIs) facilitate accurate interpretation of results. Coagulation assay results may vary by demographics and also between reagents and analyzers used. Current Thromboelastograph 6s (TEG 6s) Hemostasis Analyzer RIs were generated from adult samples.

OBJECTIVE.—

To generate reagent analyzer-specific pediatric RIs for TEG 6s and coagulation parameters.

DESIGN.—

A prospective, observational, single-center study of healthy children undergoing general anesthesia (January 3, 2017 to January 3, 2019). Venous blood samples were obtained for TEG 6s (Kaolin, Kaolin-Heparinase, Rapid and Functional Fibrinogen assays) and coagulation parameters (activated partial thromboplastin time, prothrombin time, thrombin clotting time, Echis time, antithrombin activity, and fibrinogen concentration using Instrumentation Laboratory ACL-TOP analyzers). Differences between activated partial thromboplastin time and prothrombin time reagents were investigated using mixed-effects regression, comparing maximum coefficients-of-variation with assay-specific allowable variation. RIs (lower/upper limits 2.5th of 97.5th percentiles) were generated using the following 2 methods: within discrete age-groups (neonates [<1 month], infants [1 month-1 year], young children [1-5 years], older children [6-10 years], and adolescents [11-16 years]), and modeled as functions of age and/or sex using quantile regression, including significant fractional polynomial and interaction terms.

RESULTS.—

Variation between prothrombin time and activated partial thromboplastin time assays using different reagents was clinically significant. Reagent-analyzer specific pediatric RIs were generated using data from 254 children. Discrete and model-based RIs varied by age for all coagulation parameters and TEG 6s variables in all assays.

CONCLUSIONS.—

We report reagent-analyzer specific pediatric RIs for TEG 6s and coagulation parameters. Observed variation reinforces recommendations for laboratory-specific RIs. These findings improve accuracy of interpretation of clinical results, provide a foundation for comparison and validation of tests in pathology and illustrate feasibility and advantages of model-based RI approaches.

Systematic review of viscoelastic testing (TEG/ROTEM) in obstetrics and recommendations from the women's SSC of the ISTH

Thromboelastography (TEG) and rotational thromboelastometry (ROTEM) are point-of-care viscoelastic devices that use whole blood samples to assess coagulation and fibrinolysis. These devices have been studied extensively in cardiac surgery, but there is limited robust evidence supporting its use in obstetrics. The hesitancy toward its routine use in obstetrics may be due to the current lack of randomized controlled trials and large observational studies. The study aims to systematically review studies that investigated TEG/ROTEM use in pregnancy or peripartum, and to provide recommendations for future studies to fill current research gaps. We performed a systematic review of studies on viscoelastic testing in obstetrics. Included studies were original research, used TEG or ROTEM during pregnancy or peripartum, and published in English. Ninety-three studies, spanning 31 years from 1989 to 2020 and with a total of 32,817 participants, were included. Sixty-two (66.7%) of the studies used TEG and 31 (33.3%) used ROTEM. To date, there are a total of two randomized controlled trials on TEG/ROTEM use in obstetrics. ROTEM may be used to guide transfusion therapy for postpartum hemorrhage. TEG and ROTEM can detect the hypercoagulable changes associated with pregnancy. Variability between study protocols and results suggests the need for future large prospective high-quality studies with standardized protocols to investigate the utility of TEG/ROTEM in assessing risk for thrombosis and hemorrhage as well as in guiding prophylaxis and treatment in obstetric patients. This review identifies the gaps and provides concrete recommendations for future studies to fill those gaps.

A comparative study of fibrinogen measurement using TEG® functional fibrinogen and Clauss in adolescents undergoing scoliosis surgery

INTRODUCTION

Thromboelastography (TEG®) functional fibrinogen (FF) test is a point-of-care test for fibrinogen measurement and is preferred for its rapid turnaround time. This study was designed to compare TEG® functional fibrinogen level (FLEV) with classic Clauss fibrinogen in patients undergoing scoliosis surgery and to evaluate the concordance between the two methods.

METHODS

Patients in this study were part of a larger study evaluating the effect of fibrinogen concentrate (FC) supplementation on perioperative blood loss in scoliosis surgery. Paired samples for TEG® FF and Clauss fibrinogen assays were taken from 40 patients at three different timepoints perioperatively. The agreement between FLEV and Clauss was assessed, and the possibility of using FLEV measurements to predict Clauss fibrinogen was explored.

RESULTS

One hundred and seventeen paired samples from 39 patients were finally analyzed. Pearson correlation test confirmed positive linear correlations between FLEV and Clauss at all three timepoints (r = .70, .67, and .66 at baseline, before FC administration, and after FC administration, respectively; P < .001 for all) and together for all measures (r = .76, P < .001), while Bland-Altman plots showed FLEV significantly overestimated Clauss constantly. Optimum diagnostic values of FLEV at 4.27 and 3.77 g/L were generated to predict normal fibrinogen as Clauss ≥ 3.0 g/L (AUROC 0.941, 95% CI: 0.891-0.991) and critical intraoperative hypofibrinogenemia as Clauss ≤ 2.0g/L (AUROC 0.894, 95% CI: 0.838-0.950), respectively.

CONCLUSIONS

In adolescents undergoing scoliosis surgery, FLEV correlated linearly with Clauss fibrinogen. Though FLEV overestimates Clauss constantly, FLEV values are able to predict hypofibrinogenemia and normal fibrinogen with both AUROC > 0.85.