Diagnosis of factor VIII deficiency

The role of coagulation factors VIII, IX and XI in the prediction and mediation of recurrent thrombotic events in children with non-central venous catheter deep vein thrombosis

BACKGROUND

The role of elevated coagulation factors VIII (FVIII), FIX, FXI for the prediction of recurrent thrombotic events in children after an index non-central venous catheter (non-CVC) related deep vein thrombosis (DVT) remains unclear.

OBJECTIVE

This study investigates the predictive role of FVIII, FIX, and FXI for recurrent thrombosis in children with index non-CVC DVTs, and the mediation effect of FVIII on chronic inflammation and recurrent thrombosis.

METHODS

Children aged 0-18 years diagnosed with an index non-CVC related DVT (1993-2020) were included in this single-center retrospective cohort study. Plasma levels of FVIII, FIX, FXI were measured cross-sectionally ≥30 days after the acute DVT. The association between the continuous variables FVIII, FIX, FXI and thrombosis recurrence was investigated using uni- and multivariable logistic regression, adjusting for age, sex, and chronic inflammation. Mediation analysis assessed the role of FVIII as a mediator between chronic inflammation and recurrent thrombosis. Ethics approval was obtained.

RESULTS

A total of 139 children with an index non-CVC related DVT were included. Thirty-eight (27 %) had a recurrent thrombosis at a median of 237 days (P25-P75 65-657 days) after the index DVT. In uni- and multivariable-analysis, FVIII, FIX or FXI did not predict thrombosis recurrence; However, chronic inflammation was an independent predictor. There was no evidence that FVIII mediated the effect of chronic inflammation on thrombosis recurrence.

CONCLUSION

We found no evidence that elevated FVIII, FIX or FXI predicted thrombosis recurrence, or evidence of a mediating role of FVIII. Underlying chronic inflammation predicted venous recurrent thrombotic events in this cohort.

Challenges in the Diagnosis and Management of Non-Severe Hemophilia

(1) Background: Mild and moderate hemophilia, synonymous with non-severe hemophilia (NSH), are of constant interest for the clinicians. Bleeding occurs usually after trauma, injury, surgery, or inhibitor development, sometimes leading to a shift of the clinical phenotype from mild to severe, even with life-threatening and unexpected outcomes. (2) Methods: We performed a retrospective observational study conducted on 112 persons with congenital coagulopathies, 26 of them with NSH, admitted to our clinic in the period 2000 to 2022. For the diagnosis, we used laboratory studies (complete blood cell count, coagulation assays, biochemistry, thromboelastography, genetic tests) and imaging investigations (X-ray, ultrasound, CT, MRI). We selected four cases confronted with pitfalls of diagnosis and evolution in order to illustrate the sometimes provocative field of NSH. (3) Results: Confronted with challenging cases with under-, missed or delayed diagnosis and severe consequences, we aimed at presenting four such selected cases with mild or moderate hemophilia, real pitfalls in our clinical activity. (4) Conclusions: In the field of NSH, if not timely recognized, tending sometimes to remain ignored by caregivers and patients themselves, we can be confronted with challenging diagnostic situations and life-threatening bleeds.

Population pharmacokinetic modeling of factor concentrates in hemophilia: an overview and evaluation of best practice

The accuracy of pharmacokinetic (PK)-guided dosing depends on the clinical and laboratory data used to construct a population PK model, as well as the patient’s individual PK profile. This review provides a detailed overview of data used for published population PK models for factor VIII (FVIII) and factor IX (FIX) concentrates, to support physicians in their choices of which model best suits each patient. Furthermore, to enhance detailed data collection and documentation, we do suggestions for best practice. A literature search was performed; publications describing prophylactic population PK models for FVIII and FIX concentrates based on original patient data and constructed using nonlinear mixed-effect modeling were included. The following data were collected: detailed demographics, type of product, assessed and included covariates, laboratory specifications, and validation of models. Included models were scored according to our recommendations for best practice, specifically scoring the quality of data documentation as reported. Respectively, 20 models for FVIII and 7 for FIX concentrates were retrieved. Although most models (22/27) included pediatric patients, only 4 reported detailed demographics. The wide range of body weights suggested that overweight and obese adults were represented. Twenty-six models reported the assay applied to measure factor levels, whereas only 16 models named reagents used. Eight models were internally validated using a data subset. This overview presents detailed information on clinical and laboratory data used for published population PK models. We provide recommendations on data collection and documentation to increase the reliability of PK-guided prophylactic dosing of factor concentrates in hemophilia A and B.

From Hemophilia to Deep Venous Thrombosis Patient Samples: How to Perform an Easy Coagulometer Validation Process According to Available Guidelines

Validation protocols for the evaluation of coagulometers are needed to help professionals select the most suitable system for their regular laboratory routines. The objective of this study was to show how high standard protocols for the coagulometer validation process can fit into the daily laboratory routine. For this study, 45 healthy individuals and 112 patient samples were analyzed. From the patient samples, 51 were investigated for deep venous thrombosis, 27 for coagulopathy, 19 for antivitamin K therapy, and 15 for hemophilia. For the assessment, the performance of the 3 coagulometers and 1 point-of-care device was considered. One of the coagulometers was a new acquisition evaluated for precision, linearity, throughput, and carryover in the first moment, and the new coagulometer was then compared with the other well-established equipment in the laboratory. In normal plasma, coefficient of variation was ≤1.8% for total precision in screening tests and ≤3.5% for within-run precision in specific assays. For prothrombin time/international normalized ratio, no significant difference was found when comparing methods. Our study showed how to compare the capacity of a reagent in order to discriminate patients with severe hemophilia from patients with moderated hemophilia, and the κ coefficient agreement was 0.669 (95% confidence interval: 0.3-1.0; P < .001). d-dimer evaluated in patients with deep venous thrombosis and controls showed a 20% discrepancy between the methods. In our experience across Latin America, the number of laboratories that has performed this process is limited. In this study, we demonstrated how to adapt the validation process for the hemostasis laboratory routine to help the professional chose the best and more suitable option.

Coagulation assessment with thromboelastography during abdominal endovascular aneurysm repair in a patient with hemophilia A

Background

As both APTT and APTT-based coagulation method cannot distinguish heparin effect from intrinsic coagulation factor deficiency, we implemented thromboelastography (TEG) for the coagulation assessment in a patient with hemophilia A undergoing an endovascular surgery with heparinization.

Case presentation

A 68-year-old male with hemophilia A underwent endovascular aortic repair for abdominal aortic aneurism. TEG results showed recovery of coagulation time (R) in both kaolin assay (CK) and kaolin-heparinase assay (CKH) after factor VIII replacement before heparinization. Against our expectations, R-CKH was slightly prolonged (9.0 min) during heparinization. After the administration of protamine sulfate, R in both assays showed similar values within the normal ranges.

Conclusions

The combination of CK and CKH assays could be useful to estimate factor VIII (FVIII) level when heparin concentration is low or without heparin; however, caution should be necessary for estimation of FVIII level by TEG under the effect of medium- or high-dose heparin.

The central role of thrombin in bleeding disorders

Maintaining normal hemostasis relies on a regulated system of procoagulant and anticoagulant pathways, and disruption of these processes leads to the loss of hemostatic control, with the potential for excessive bleeding or thrombosis. Evaluation of bleeding disorders has conventionally been achieved by laboratory assays that measure the activity of individual coagulation factors. While such assays have proven effective for detecting abnormalities of the coagulation system and aiding diagnosis, inherent limitations prevent them from capturing a complete picture of hemostatic function. An improved understanding of thrombin activity and its central role in hemostasis and bleeding disorders has led to the clinical development of global assays that are more physiologically relevant than traditional assays; furthermore, these global assays are able to monitor responses to therapy. In this review, we provide an overview of the role of thrombin in hemostasis, and describe the clinical benefits of thrombin monitoring in patients with bleeding disorders. Moreover, we discuss recent advances in thrombin-targeting therapeutic strategies that aim to correct thrombin deficiency and prevent bleeding in patients with hemophilia and other rare bleeding disorders.

Evaluation of an automated chromogenic assay for Factor VIII clotting activity measurement in patients affected by haemophilia A

INTRODUCTION

The original one-stage clotting assay is still the most widely used method to measure Factor VIII clotting activity (FVIII:C) in patients with haemophilia A (HA), although the use of chromogenic assays is increasing significantly.

AIM

Evaluation of the analytical performance and diagnostic accuracy of BIOPHEN™ FVIII:C (HYPHEN BioMed, Neuville-sur-Oise, France) assay on Sysmex CS-2400 (Sysmex, Kobe, Japan) analyser.

METHODS

Sixty patients with haemophilia A (HA; any severity) and 120 healthy Italian subjects were included. All the assays were performed on citrate platelet-poor plasmas stored at -80°C. Chromogenic BIOPHEN™ FVIII:C was compared with the one-stage assay using Actin FS and Factor VIII deficient plasma (Siemens Healthcare Diagnostics, Marburg, Germany) on Sysmex CS-2400 and with another chromogenic automated assay (COAMATIC™ Factor VIII, CHROMOGENIX on ACL TOP analyzer; Instrumentation Laboratory, Milan, Italy).

RESULTS

Intra-assay and inter-assay coefficient of variation were <6%. Linearity was good up to 1/128 dilution (r = 0.99); mean recovery was 91.7% and limit of detection was 0.2%. BIOPHEN™ FVIII:C assay showed a good correlation and diagnostic agreement with the chromogenic COAMATIC™ assay: the Spearmen's Rank correlation coefficient was 0.98 and the inter-rate agreement K Cohen coefficient was 0.61. The K coefficient was 0.91 when BIOPHEN™ FVIII:C was compared with the historical classification of the patients, demonstrating an optimal diagnostic accuracy in HA.

CONCLUSIONS

BIOPHEN™ FVIII:C showed good analytical performance and diagnostic accuracy and could be considered suitable for the introduction in routine analytical panel of coagulation for the diagnosis of HA patients.

Analytical variation in factor VIII one-stage and chromogenic assays: Experiences from the ECAT external quality assessment programme

Background

Both one‐stage (OSA) and chromogenic substrate assays (CSA) are used to measure factor VIII (FVIII) activity. Factors explaining analytical variation in FVIII activity levels are still to be completely elucidated.

Aim

The aim of this study was to investigate and quantify the analytical variation in OSA and CSA.

Methods

Factors determining analytical variation were studied in sixteen lyophilized plasma samples (FVIII activity <0.01‐1.94 IU/mL) and distributed by the ECAT surveys. To elucidate the causes of OSA variation, we exchanged deficient plasma between three company set‐ups.

Results

On average, 206 (range 164‐230) laboratories used the OSA to measure FVIII activity and 30 (range 12‐51) used CSA. The coefficient of variation of OSA and CSA increased with lower FVIII levels (FVIII <0.05 IU/mL). This resulted in misclassification of a severe haemophilia A sample into a moderate or mild haemophilia A sample in 4/30 (13.3%) of CSA measurements, while this was 37/139 (26.6%) for OSA. OSA measurements performed with reagents and equipment from Werfen showed slightly lower FVIII activity (0.93, IQR 0.88‐0.98 IU/mL) compared to measurements with Stago (1.07, IQR 1.02‐1.14 IU/mL) and Siemens (1.03, IQR 0.97‐1.07 IU/mL). Part of this difference is explained by the value of the calibrator. For CSA, the measured FVIII levels were similar using the different kits.

Conclusions

In the lower range (<0.05 IU/mL), analytical variation of FVIII measurements is high in both OSA and CSA measurements. The variation in FVIII activity levels was partly explained by specific manufacturers. Further standardization of FVIII measurements and understanding of analytical variation is required.

Shifting Landscape of Hemophilia Therapy: Implications for Current Clinical Laboratory Coagulation Assays

Clinical coagulation assays are an integral part of diagnosing and managing patients with hemophilia; however, in this new era of bioengineered factor products and non-factor therapeutics, problems have arisen with use of traditional coagulation tests for the quantification of several of these new products. Discussion over the use of one-stage clotting assays versus chromogenic substrate assays for clinical decision making and potency labeling has been ongoing for many years. Emerging factor concentrates have heightened concern over assay selection and availability. Emicizumab interferes with all aPTT based assays, rendering them unreliable and potentially falsely reassuring to the unaware provider. This review explores considerations for coagulation assays in the clinical setting and highlights how awareness of institutional coagulation assays and potential limitations have never been more critical for providers caring for patients with bleeding disorders. This article is protected by copyright. All rights reserved.

One-Stage Factor VIII Assays

Coagulation factor assays using one-stage methodology are widely used to measure factor levels for the purpose of detecting a deficiency, or to monitor replacement therapy. In this chapter, we focus on a method to measure Factor VIII coagulant activity (FVIII:C) by the one-stage assay (FVIII:C-1), with extra information provided to also allow this method to apply to Factor IX (FIX), Factor XI (FXI), and Factor XII (FXII). From the perspective of laboratory testing, these factors are components of the "intrinsic" coagulation pathway and are all measured in test systems based on the correction of the Activated Partial Thromboplastin Time (APTT). Factor activity is assessed by measuring the ability of an unknown sample to correct the prolonged APTT of factor-deficient plasma (deficient in the factor of interest), relative to the effect of a known calibrator. These assays are used for the diagnosis of the many causes of reduced factor levels, including those causing a prolonged APTT. It is important for laboratory staff to understand the impact of method variations, limitations, and result interpretation and these aspects are also discussed.

The thrombin generation assay distinguishes inhibitor from non-inhibitor patients with severe haemophilia A

INTRODUCTION

Patients with haemophilia A (HA) have impaired thrombin generation (TG) capacity and TG assay (TGA) values are linearly related to plasma factor VIII (FVIII) levels.

AIM

This study carried out in patients with unmeasurable FVIII (<1 IU dL(-1) ) was aimed at unravelling any difference in TG capacity in patients with or without inhibitors.

METHODS

Blood samples were collected from patients in a non-bleeding state, after a 5-day wash-out period from last treatment.

RESULTS

TGA was performed in 102 patients with severe HA (15% with high-responding inhibitors; 51% with null F8 mutations, that as expected were more prevalent in inhibitor than in non-inhibitor patients). TG capacity was significantly lower in inhibitor than non-inhibitor patients and in those with null mutations than in those with non-null mutations. When the TG capacity was evaluated only in patients with null mutations with and without inhibitors it was lower in the presence of inhibitors.

CONCLUSIONS

This study shows a greater TG impairment in inhibitor patients irrespective of FVIII levels, inhibitor titre and F8 mutation type, suggesting a role for the TGA in unravelling functional interferences of anti-FVIII inhibitors on coagulation system activation.

Specific and global coagulation tests in patients with mild haemophilia A with a double mutation (Glu113Asp, Arg593Cys)

BACKGROUND

Heterogeneous bleeding phenotypes are observed in haemophilia A patients with the same mutation in the F8 gene. Specific mutations in the A2 domain of factor VIII are associated with mild haemophilia and a higher risk of inhibitor development. Double mutations in mild haemophilia A are rarely reported. In this study, we investigated the in vitro function of factor VIII, performing different specific and global coagulation assays, observed clinical characteristics and assessed the possible predictive diagnostic value of the differences.

MATERIALS AND METHODS

The clinical features of haemophiliacs with a mild phenotype were reviewed. Blood samples were obtained and analysed for mutations and coagulation assays: activated partial thromboplastin time, one-stage and chromogenic factor VIII activity, factor VIII antigen and rotational thromboelastometry.

RESULTS

We report on a cohort of 22 patients with double Glu113Asp, Arg593Cys mutations. All our patients have a quantitative defect of factor VIII and preserved similar functional activity. Factor VIII activities measured by the one-stage or chromogenic method were not discrepant, although the chromogenic assay resulted in 20% lower factor VIII activities. Waveform analysis showed a lower maximum value of the second derivative curve (Max2) of APTT with curve shape alternation, while thromboelastometry (INTEM) showed low sensitivity in comparison to results in a normal population.

DISCUSSION

In genotyping, the coexistence of a second mutation should never be excluded, especially in cases of discordant clinical presentation. Waveform analysis correlates better with factor VIII activity than thromboelastometry and the Max2 parameter could provide additional information in managing haemophilia patients. The utility of specific factor activity and global haemostatic assays in general practice still needs to be investigated.

Perils, problems, and progress in laboratory diagnosis of von Willebrand disease

Diagnosis of von Willebrand disease (VWD) merits consideration of personal and family history of bleeding symptoms along with confirmatory laboratory testing. As the latter yields quantifiable results, overreliance on a laboratory diagnosis may occur. However, existing tests for VWD contain potential sources for error. Both intrinsic and extrinsic factors affecting these assays can contribute to either falsely normal or falsely abnormal results. This article will discuss the present available assays as well as new developments in diagnostic testing. A clear understanding of the limitations of VWD testing is helpful for ensuring the correct diagnosis of affected patients.

Comparative field study evaluating the activity of recombinant factor VIII Fc fusion protein in plasma samples at clinical haemostasis laboratories

Discrepancies exist for some of the modified coagulation factors when assayed with different one-stage clotting and chromogenic substrate assay reagents. The aim of this study was to evaluate the performance of a recombinant factor VIII Fc fusion protein (rFVIIIFc), currently in clinical development for the treatment of severe haemophilia A, in a variety of one-stage clotting and chromogenic substrate assays in clinical haemostasis laboratories. Haemophilic plasma samples spiked with rFVIIIFc or Advate® at 0.05, 0.20 or 0.80 IU mL⁻¹ were tested by 30 laboratories using their routine procedures and plasma standards. Data were evaluated for intra- and inter-laboratory variation, accuracy and possible rFVIIIFc-specific assay discrepancies. For the one-stage assay, mean recovery was 95% to 100% of expected for both Advate® and rFVIIIFc at 0.8 IU mL⁻¹. Intra-laboratory percent coefficient of variance (CV) ranged from 6.3% to 7.8% for Advate®, and 6.0% to 10.3% for rFVIIIFc. Inter-laboratory CV ranged from 10% for Advate® and 16% for rFVIIIFc at 0.8 IU mL⁻¹, to over 30% at 0.05 IU mL⁻¹ for both products. For the chromogenic substrate assay, the average FVIII recovery was 107% ± 5% and 124% ± 8% of label potency across the three concentrations of Advate® and rFVIIIFc, respectively. Plasma rFVIIIFc levels can be monitored by either the one-stage or the chromogenic substrate assay routinely performed in clinical laboratories without the need for a product-specific rFVIIIFc laboratory standard. Accuracy by the one-stage assay was comparable to that of Advate®, while marginally higher results may be observed for rFVIIIFc when using the chromogenic assay.

The factor VIII inhibitor assays can be standardized: results of a workshop

BACKGROUND

The Bethesda and the Nijmegen assays are commonly used for the measurement of inhibitor levels in hemophilia A patients. Despite test innovations, the between-laboratory coefficient of variation (CVb) of factor VIII inhibitor test data in external quality surveys remains very high (40-60%) with a high degree of false-negative and false-positive results resulting in undesired effects on treatment.

OBJECTIVES

Organization of a workshop in order to address the causes of this phenomenon and to suggest ways to improve the assays.

METHODS

Fifteen laboratories showing a high CVb in regular surveys and using a variety of methods participated in the wet workshop, which included four different sessions where variables probably contributing to the high CVb (e.g. use of [non-]buffered plasma, FVIII-deficient plasma, sample dilution and APTT reagents) were investigated.

RESULTS

The CVb varied from 30% to 70% in the first session of the workshop when the participants used their own test settings and reagents. The use of buffered normal pooled plasma and FVIII-deficient plasma as a reference sample by all participants did not significantly alter the CVb (35-50%) but decreased the number of false positives. However, the use of buffered pooled plasma in combination with standardized sample dilution procedures by all participants showed a significant improvement (CVb, 10-20%).

CONCLUSIONS

These results may contribute to improvement of FVIII inhibitor testing. However, improved inter-laboratory comparison of factor VIII inhibitor assay results can only be reached when further local standardization is implemented.

Pharmacotherapy of haemophilia A

INTRODUCTION

Haemophilia A is due to factor VIII (FVIII) deficiency. The main treatment is replacement therapy with FVIII concentrates. However, these concentrates carried a high risk of blood-borne viral infections and still have a high risk of inducing anti-FVIII inhibitors.

AREAS COVERED

An overview of products available and therapeutic options for haemophilia A management in order to help in decision making. A literature search using Medline with the keywords: 'haemophilia', 'factor VIII', 'therapy', 'inhibitor', 'concentrate', 'bleeding', 'prophylaxis', 'on demand', 'plasma-derived', 'recombinant', 'coagulation factors', 'immunotolerance' was performed. The years 1960 - 2010 are included.

EXPERT OPINION

Progress in management of patients with haemophilia A has allowed increased life expectancy and quality of life. There is evidence that prophylaxis prevents or, at least, slows down arthropathy development when started early in childhood. FVIII concentrates have achieved high levels of blood-borne pathogen safety. However, treatment is frequently complicated by development of FVIII-neutralizing inhibitors, which prevent control of bleeding and predispose to a high morbidity and mortality risk. Bypassing agents are effective in bleeding treatment in a high percentage of cases. Prophylaxis with bypassing agents and their use in combination are offering opportunities in management of inhibitor patients. More evidence is necessary to understand how to prevent and manage this complication.

Mild hemophilia A

Mild hemophilia A (HA), defined by clinical features and factor VIII coagulant activity (FVIII:C) between 0.05 and 0.40 IU mL(-1), is characteristically distinct from severe HA. Indeed, although the molecular characterization of mild HA has permitted the identification of specific underlying mutations, its clinical phenotype is strikingly different from that of patients with a severe FVIII defect, where spontaneous hemorrhages or recurrent joint bleeding are usual manifestations. With aging, mild HA patients may develop complications (i.e. cancers and cardiovascular disorders), the management of which may prove challenging due to the concomitant bleeding tendency. Furthermore, the development of inhibitors provides an additional major complication in these patients, because it increases the severity of the bleeding phenotype and complicates their management. Standard management of mild HA includes the use of desmopressin and antifibrinolytic agents for minor bleeding episodes or surgical procedures, whilst major bleeding or surgery requires replacement therapy with FVIII concentrates. As regards treatment of patients with inhibitors, bypassing agents (i.e. activated prothrombin complex concentrates and recombinant activated FVII) have proven effective in the treatment of bleeding episodes, but as there are insufficient data to determine the optimal approach to immune tolerance induction in this group of patients, their optimal management remains controversial. Rituximab is a newer, promising therapeutic option for inhibitor eradication in such patients. Many aspects concerning mild HA remain to be clarified, including the molecular basis, the natural history and the optimal diagnostic and therapeutic strategies. Only large prospective studies will shed light on this condition.

The laboratory approach to inherited and acquired coagulation factor deficiencies

Besides the long-recognized hemophilias, there are many other factor deficiencies. Some also are inherited, but others are acquired because of both immune and nonimmune etiologies. Understanding the optimal laboratory approach to evaluating factor deficiency will aid physicians and laboratory scientists in obtaining a prompt diagnosis and in avoiding pitfalls in coagulation testing.