Factor VIII activity of BAY 94-9027 is accurately measured with most commonly used assays: Results from an international laboratory study.

INTRODUCTION: Discrepancies in the measurement of modified factor VIII (FVIII) products have been recognized, highlighting the need for adjustments in clinical laboratory practices to ensure effective monitoring of patients treated with these products, particularly using the one-stage (activated partial thromboplastin time [aPTT]) assay. AIM: To assess the ability of clinical laboratories to measure the activity of BAY 94-9027, a PEGylated extended half-life FVIII product, using routine (predominantly one-stage) assays in clinical laboratories METHODS: Blinded samples of FVIII-deficient plasma spiked with defined levels of BAY 94-9027 and a recombinant FVIII product comparator were provided to 52 clinical laboratories that routinely conduct FVIII testing. Samples were provided at 3 concentrations (low, medium and high), and laboratories analysed the samples using routine in-house one-stage and, when available, chromogenic assays. Acceptable spiked recovery (accuracy) of the local laboratory methods to measure BAY 94-9027 was the primary endpoint of the study. RESULTS: Accurate FVIII measurements were obtained at all concentrations for both products using the chromogenic assay and most of the commonly used one-stage reagents, both ellagic acid and silica based. Two specific silica-based reagents, APTT-SP and PTT-A, underestimated BAY 94-9027 levels at all concentrations, consistent with previous findings. CONCLUSIONS: FVIII activity of BAY 94-9027 was accurately measured with most commonly used one-stage assays used in routine clinical practice. The chromogenic assay was also accurate. It is recommended that clinical laboratories identify and avoid specific inappropriate reagents, such as the APTT-SP and PTT-A, in their one-stage assays for FVIII monitoring.

Measuring FVIII activity of glycopegylated recombinant factor VIII, N8-GP, with commercially available one-stage clotting and chromogenic assay kits: a two-centre study.

INTRODUCTION: Factor VIII activity (FVIII:C) assays of samples containing glycoPEGylated recombinant FVIII such as turoctocog alfa pegol (N8-GP) can be associated with differences in FVIII recovery in vitro between various one-stage activated partial thromboplastin time (APTT)-based clotting assays and some chromogenic assays. Careful validation and qualification of specific assays and conditions is therefore necessary for the assessment of FVIII:C in samples containing modified FVIII molecules. AIM: To assess the ability of various one-stage clotting and chromogenic FVIII:C assays to measure samples containing N8-GP compared to unmodified recombinant FVIII (rFVIII) across two laboratory sites. METHODS: Factor VIII activity in severe haemophilia A (HA) plasma spiked with a range of concentrations (from low, 0.20 IU mL-1 , to high, 0.90 IU mL-1 ) of N8-GP and rFVIII, was determined at two laboratory sites using 12 commercially available one-stage clotting and chromogenic FVIII:C assays. Assays were performed using a plasma calibrator and different analysers. RESULTS: Acceptable N8-GP recovery was observed in the low to high concentration samples tested using the majority of the tested APTT reagents with only one reagent causing a significant underestimation as compared to rFVIII. For the chromogenic assays, a slight overestimation was observed with some of the kits. Variability between the two laboratory sites are likely attributable to the use of different analysers with the respective APTT reagents. CONCLUSIONS: These results highlight the need to investigate the performance of modified factor products using standard assays. The performance of different one-stage clotting assays, APTT reagents, reference calibrators and instrumentation should also be evaluated.

Recombinant to modified factor VIII and factor IX - chromogenic and one-stage assays issues.

The recent development of modified recombinant factor VIII (FVIII) and factor IX (FIX) therapeutic products with extended half-lives will create challenges for the haemostasis laboratory in obtaining recovery estimates of these products in clinical samples using existing assays. The new long-acting therapeutic concentrates contain molecular modifications of Fc fusion, site-specific of polyethylene glycol or albumin fusion. The optimum methods for monitoring each new product will need to be assessed individually and laboratories should select an assay which gives similar results to the assay used to assign potency to the product in question. For some extended half-life FVIII and FIX products some one stage assays are entirely unsuitable for monitoring purposes. For most products and assay reagents studied so far, and reviewed in this manuscript, chromogenic FVIII or FIX assays can be safely used with conventional plasma standards. If one stage assays are used then they should be performed using carefully selected reagents/methods which have been shown to recover activity close to the labelled potency for the specific product being monitored.

Factor VIII assay variability in postinfusion samples containing full length and B-domain deleted FVIII.

INTRODUCTION: Although the variability in factor VIII (FVIII):C measurement is well recognized, this has not been widely reported for post-FVIII infusion samples. AIM/METHODS: Three samples from haemophilia A patients were distributed in a UK National External Quality Assessment Scheme survey, each after treatment with either ReFacto AF, Kogenate FS or Advate. Fifty-two UK haemophilia centres performed FVIII assays using one-stage (n = 46) and chromogenic (n = 10) assays. Centres calibrated assays with the local plasma standard and with ReFacto AF laboratory standard for the ReFacto AF sample. RESULTS/CONCLUSIONS: Chromogenic assays gave significantly higher results than one-stage assays (P < 0.0001, 32% difference) in the post-Kogenate sample but not in the post-ReFacto AF (11% higher by chromogenic assay, ns) or post-Advate samples (3% lower by chromogenic, ns) when assays were calibrated with plasma standards. Twenty centres used all Instrumentation Laboratory (IL)-activated partial thromboplastin time reagents (Synthasil)/IL deficient plasma/reference plasma) in the one-stage assay and 15 used all Siemens reagents (Actin FS/Siemens deficient plasma/reference plasma); this made a significant difference to results post-ReFacto AF (41% higher by IL reagents, P < 0.0001) and Advate (39% higher by IL reagents, P < 0.0001), but not Kogenate (7% higher by IL, ns) when calibrated with plasma standards. Differences between results obtained with different one-stage assay reagents for monitoring Advate have implications for dosing patients. Furthermore, there was considerable inter-laboratory variation as indicated by CVs in the range 15-26% for chromogenic assay and 12-19% for one-stage assay results. This study suggests that external quality assessment schemes should offer participation in post-FVIII infusion schemes where haemophilic patients are monitored.

BAY 81-8973, a full-length recombinant factor VIII: results from an International comparative laboratory field study.

INTRODUCTION: BAY 81-8973 is a full-length, unmodified, recombinant human factor VIII (FVIII) with the same primary amino acid sequence as sucrose-formulated recombinant FVIII but produced with certain more advanced manufacturing technologies. AIM: This global laboratory study evaluated variability in measurement of BAY 81-8973 using one-stage and chromogenic assays compared with antihaemophilic factor (recombinant) plasma/albumin-free method (rAHF-PFM; Advate(®) ) under assay conditions routinely used in clinical laboratories. METHODS: BAY 81-8973 or rAHF-PFM was spiked into FVIII-deficient plasma at 0.043 (low), 0.375 (medium) and 0.865 (normal) IU mL(-1) . Participating laboratories analysed blinded samples and normal plasma in triplicate using their routine assay, reagents and standards. Results were analysed for intra- and interlaboratory variability. RESULTS: Forty-one laboratories in 11 countries participated in the study. One-stage assay and chromogenic assays were used by 40 and 10 laboratories, respectively; 9 laboratories used both assays. Intralaboratory variability was <11% for both assays and both products at all concentrations. Interlaboratory variability was highest at the low concentration in the chromogenic and one-stage assay for BAY 81-8973 (60.0% and 33.7%, respectively) and rAHF-PFM (51.0% and 30.8%) and was lowest at the normal concentration (BAY 81-8973, 5.4% and 14.0%; rAHF-PFM, 5.8% and 12.4%), which was similar to the plasma control (6.6% and 10.3%). The chromogenic:one-stage assay ratio ranged from 0.95 (low concentration) to 1.10 (normal concentration) for BAY 81-8973 and 0.96-1.18 for rAHF-PFM. CONCLUSIONS: BAY 81-8973 can be accurately measured in plasma using the one-stage and chromogenic assays routinely used in clinical laboratories without a product-specific standard.

Current laboratory practices in the diagnosis and management of haemophilia: a global assessment.

Haemophilia management is complicated by the extreme variability in laboratory practices. Lack of consistency or comparability in testing makes it difficult to establish diagnostic criteria or disease severity, and complicates response assessment. A global survey was conducted to document current practices. A 35-min survey was completed by 30 laboratory scientists in each of seven countries (France, Germany, Italy, Japan, Spain, UK, USA; 210 in total); results were weighted by average country testing volume in haemophilia. Eighty-three per cent of participants reported participation in a Quality Assurance scheme. Ninety per cent reported using clotting tests in haemophilia A and 88% in haemophilia B (55% and 53% frequent use respectively). Sixty-eight per cent reported chromogenic assays were used in haemophilia A, with only 23% reporting frequent use, compared to only 11% reporting any use in haemophilia B. Twenty-nine separate activated partial thromboplastin time (aPTT) reagents were reported for haemophilia A and 27 aPTT reagents were reported for haemophilia B, with one-quarter or less obtaining reagents or kits from any single manufacturer. Fifty-four per cent run a calibration curve with every factor VIII (FVIII) assay. The mean number of plasma dilutions varied from 2 to 4 for FVIII assays and from 1 to 3 for FIX assays. Results indicate very low consistency in materials and practices used to test for factor activity in haemophilia. A number of responses suggest that some laboratory scientists' understanding of best practices or guidelines in haemophilia could be improved. More education and broader understanding is recommended regarding assay types, assay components, test material and instrument features and capabilities.

Monitoring of modified factor VIII and IX products.

The dawning era of novel recombinant factor VIII and factor IX concentrates, many of which have been bioengineered to achieve prolonged activity, brings with it the need to consider the most appropriate clinical laboratory approaches for potency assignment, as well as the measurement of postinfusion levels. This session will highlight the known limitations and inconsistencies between existing assay methodologies with respect to currently available products, and discuss some of the early data with respect to the novel agents.

Guidelines for the management of hemophilia.

Hemophilia is a rare disorder that is complex to diagnose and to manage. These evidence-based guidelines offer practical recommendations on the diagnosis and general management of hemophilia, as well as the management of complications including musculoskeletal issues, inhibitors, and transfusion-transmitted infections. By compiling these guidelines, the World Federation of Hemophilia aims to assist healthcare providers seeking to initiate and/or maintain hemophilia care programs, encourage practice harmonization around the world and, where recommendations lack adequate evidence, stimulate appropriate studies.

Standards and monitoring treatment.

Accuracy and reproducibility of laboratory measurements are important in the diagnosis and treatment of bleeding disorders. This article describes the process of establishment of international standards and some of the problems that have arisen in standardization of these measurements.

Genetics of haemostasis.

Congenital defects of platelets or plasma proteins involved in blood coagulation generally lead to bleeding disorders. In some of these disorders, patients with a severe phenotype are prone to spontaneous bleeds with critical consequences. This situation occurs more commonly in haemophilia A and haemophilia B and to a certain extent in severe forms (type 3) of von Willebrand disease. Defects in other plasma coagulation proteins and platelet factors are relatively rare, with an incidence of ≤ 1: 1-2 million. Molecular genetic studies of the human coagulation factors, especially factors VIII and IX, have contributed to a better understanding of the biology of these genetic disorders, the accurate detection of carriers and genetic counselling, and have also fostered new therapeutic strategies. This article reviews the evolution of genetics over the last five decades as a tool for bleeding disorder investigations, the recent advances in molecular techniques that have contributed to improved genetic diagnosis of this condition, and the development and utility of proficiency testing programmes and reference materials for genetic diagnosis of bleeding disorders.

Generation of HIV latency during thymopoiesis.

The use of combination antiretroviral therapy results in a substantial reduction in viremia, a rebound of CD4+ T cells and increased survival for HIV-infected individuals. However, this treatment does not result in the total eradication of HIV. Rather, the virus is thought to remain latent in a subset of cells, where it avoids elimination by the immune system. In this state the virus is capable of reactivation of productive infection following cessation of therapy. These latently infected cells are very few in number and it has thus been difficult to determine their origin and to study the molecular nature of the latent viral genome. HIV replication is linked to cellular gene transcription and requires target cell activation. Therefore, should an activated, infected cell become transcriptionally inactive prior to cytopathic effects, the viral genome might be maintained in a latent state. We used the SCID-hu (Thy/Liv) mouse model to establish that activation-inducible HIV can be generated at high frequency during thymopoiesis, a process where previously activated cells mature towards quiescence. Moreover, we showed that these cells can be exported into the periphery where the virus remains latent until T-cell receptor stimulation, indicating that the thymus might be a source of latent HIV in humans.

ApoA-I mimetics favorably impact cyclooxygenase 2 and bioactive lipids that may contribute to cardiometabolic syndrome in chronic treated HIV.

OBJECTIVE: We investigated whether apolipoprotein A-I (apoA-I) mimetic peptides 4F and 6F can be a novel therapeutic strategy to reduce blood and gut bioactive lipids, proinflammatory effects of endotoxin (LPS) and aberrant activation of cyclooxygenase 2 (COX-2) as instigators of increased risk for cardiometabolic disease in chronic treated HIV. METHODS: We used two humanized murine models of chronic treated HIV infection (n = 109 mice) and gut explants from HIV infected (n = 10) persons to determine whether Tg6F and 4F attenuate in vivo and ex vivo increased blood and gut bioactive lipids (measured by mass spectrometry) and intestinal protein levels of COX-2 (measured by immunoassays) in chronic treated HIV. RESULTS: In these models of HIV, when compared to HIV-1 infected mice on antiretroviral therapy (ART) alone, oral Tg6F in combination with ART attenuated increases in plasma and gut bioactive lipids (and particularly COX lipids) and intestinal COX-2. 4F and Tg6F also reduced ex vivo production of COX-2 protein and associated secretion of bioactive lipids in gut explants from HIV-1 infected persons treated with LPS. CONCLUSION: ApoA-I mimetics favorably impact the proinflammatory effects of LPS, COX-2 and production of bioactive lipids that collectively drive gut and systemic inflammation in chronic treated HIV. Given prior experimental evidence that the proinflammatory effects of LPS, COX-2 and gut dysfunction contribute to cardiometabolic syndrome in chronic HIV, apoA-I mimetic peptides may be a novel therapy to treat cardiometabolic syndrome in chronic HIV.

Human immunodeficiency virus 1 envelope proteins induce interleukin 1, tumor necrosis factor alpha, and nitric oxide in glial cultures derived from fetal, neonatal, and adult human brain.

Although microglia are the only cells found to be productively infected in the central nervous system of acquired immunodeficiency disease syndrome (AIDS) patients, there is extensive white and gray matter disease nonetheless. This neuropathogenesis is believed to be due to indirect mechanisms other than infection with human immunodeficiency virus 1 (HIV-1). Cytokines and toxic small molecules have been implicated in the clinical and histopathological findings in CNS AIDS. Previously, we have demonstrated in rodent glial cultures the presence of biologically active epitopes of gp120 and gp41 that are capable of inducing interleukin 1 and tumor necrosis factor alpha. In this study, we map the HIV-1 envelope epitopes that induce nitric oxide, inducible nitric oxide synthase, interleukin 1, and tumor necrosis factor alpha in human glial cultures. Epitopes in the carboxy terminus of gp120 and the amino terminus of gp41 induce these proinflammatory entities. In addition, we compare HIV-1 infection and pathology in glial cells derived from human brain taken at different states of maturation (fetal, neonatal, and adult brain) in an effort to address some of the clinical and histological differences seen in vivo. This study demonstrates that, in the absence of virus infection and even in the absence of distinct viral tropism, human glia respond like rodent glia to non-CD4-binding epitopes of gp120/gp41 with cytokine and nitric oxide production. Differences among fetal, neonatal, and adult glial cells' infectivity and cytokine production indicate that, in addition to functional differences of glia at different stages of development, cofactors in vitro and in vivo may also be critical in facilitating the biological responses of these cells to HIV-1.

STAGdb: a 30K SNP genotyping array and Science Gateway for Acropora corals and their dinoflagellate symbionts.

Standardized identification of genotypes is necessary in animals that reproduce asexually and form large clonal populations such as coral. We developed a high-resolution hybridization-based genotype array coupled with an analysis workflow and database for the most speciose genus of coral, Acropora, and their symbionts. We designed the array to co-analyze host and symbionts based on bi-allelic single nucleotide polymorphisms (SNP) markers identified from genomic data of the two Caribbean Acropora species as well as their dominant dinoflagellate symbiont, Symbiodinium 'fitti'. SNPs were selected to resolve multi-locus genotypes of host (called genets) and symbionts (called strains), distinguish host populations and determine ancestry of coral hybrids between Caribbean acroporids. Pacific acroporids can also be genotyped using a subset of the SNP loci and additional markers enable the detection of symbionts belonging to the genera Breviolum, Cladocopium, and Durusdinium. Analytic tools to produce multi-locus genotypes of hosts based on these SNP markers were combined in a workflow called the Standard Tools for Acroporid Genotyping (STAG). The STAG workflow and database are contained within a customized Galaxy environment (https://coralsnp.science.psu.edu/galaxy/), which allows for consistent identification of host genet and symbiont strains and serves as a template for the development of arrays for additional coral genera. STAG data can be used to track temporal and spatial changes of sampled genets necessary for restoration planning and can be applied to downstream genomic analyses. Using STAG, we uncover bi-directional hybridization between and population structure within Caribbean acroporids and detect a cryptic Acroporid species in the Pacific.

Laboratory performance in the World Federation of Hemophilia EQA programme, 2003-2008.

External quality assessment (EQA) has been shown to improve laboratory performance and diagnosis in haemostasis. We report here findings from the World Federation of Haemophilia (WFH) EQA programme during the period 2004-2007. Samples for PT, APTT, FVIII:C, FIX:C and VWF assays were distributed to centres in both established and emerging countries, and results were compared with results obtained by United Kingdom National External Quality Assessment Scheme (UK NEQAS) participants on the same samples. In general, good agreement was seen throughout between WFH and UK NEQAS for screening tests, and it was possible to identify an improvement in WFH centre agreement for results for VWF assays during the period of study. Agreement between emerging and established WFH centres was comparable for screening tests, possibly indicative of the relative simplicity of these tests and the degree of automation now employed in almost all haemostasis laboratories. However, CVs and performance compared with UK NEQAS participant results for factor assays amongst established centres was better than between emerging centres. Distribution of a questionnaire revealed different application of methodology for these assays, which may contribute to the observed difference in performance. Several centres participated in supplementary exercises, with comparable results obtained by emerging and established centres performing FVIII and fibrinogen measurement on cryoprecipitate, and all centres performing FVIII inhibitor assays correctly identifying the presence of an inhibitor. Participation in EQA programmes should continue to encourage improvement in laboratory performance and therefore improvements in the diagnosis and care of patients with haemophilia.

The use of ecarin chromogenic assay and prothrombinase induced clotting time in the monitoring of lepirudin for the treatment of heparin-induced thrombocytopenia.

Lepirudin (r-hirudin) is one of the two alternative anticoagulants licensed to treat patients with heparin-induced thrombocytopenia (HIT). Manufacturer's guidelines state that lepirudin should be monitored using the activated partial thromboplastin time (APTT) ratio. However, several studies have demonstrated a plateau effect of higher concentrations of lepirudin on APTT ratios and variable results when comparing different APTT reagents. This study compares APTT ratios (using two different APTT reagents) with two other commercially available methods for directly quantifying plasma lepirudin levels: ecarin chromogenic assay and prothrombinase-induced clotting time in 95 samples from five patients receiving lepirudin anticoagulation for HIT.

Wide variation in thrombin generation in patients with atrial fibrillation and therapeutic International Normalized Ratio is not due to inflammation.

Atrial fibrillation (AF) is a common cardiac arrhythmia with a 5-20% annual risk of stroke. Warfarin reduces this risk by at least 60%. Despite adequate anticoagulation within the target International Normalized Ratio (INR) range of 2.0-3.0, some patients still experience thrombotic and bleeding events. It is now possible to assess the intensity of anticoagulation with automated thrombin generation (TG) tests, such as the calibrated automated thrombogram (CAT). These tests were compared and an inverse relationship was found between the INR and CAT in 143 elderly AF patients. There was equally good correlation between the concentration of factors II, VII, IX and X and the INR and TG parameters. The peak thrombin was most strongly associated with the concentration of prothrombin fragment 1 + 2 in plasma. There was wide variability in TG parameters in patients with identical INR values, sometimes up to a fourfold difference. This TG variability in individuals with the same INR is not due to inflammation, at least when the latter is measured as the concentration of factor VIII coagulant activity, von Willebrand factor antigen, high sensitivity C-reactive protein and fibrinogen. It was concluded that, although the TG and INR were closely correlated there was wide variability in peak thrombin and endogenous thrombin potential in patients within the INR therapeutic range, the cause of which remains unclear.