Laboratory Assays in Hemophilia

Ingerslev, Jørgen

doi:10.1002/9780470987124.ch41

Cited by 8 publications

(11 citation statements)

References 25 publications

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“…A burst of thrombin formation occurs after sufficient levels of activated FVIII (FVIIIa) have been generated through feedback activation by thrombin, leading to the formation of a clot. 5 The one-stage factor activity assay can be used to measure intrinsic pathway FVIII, FIX or FXI activity, 11,12 in addition to FXII, HMWK and PK activities. The factor being investigated is the only limiting factor in this type of assay; all reagents, except the type of deficient plasma used, and the methodology remain constant.…”

Section: One-stage Aptt-based Factor Activity Assaysmentioning

confidence: 99%

“…13 All standards (calibrators) should be traceable against an international standard (IS), known as a primary standard. 11,13 Laboratorymanufactured standards are usually traceable to a secondary standard that has been calibrated against the primary standard. It is recommended that factor activity assays are calibrated at a minimum of once every 6 months, although calibrations are required for new lots of reagents (both deficient plasma and APTT reagents), and some laboratories calibrate more often.…”

Section: One-stage Aptt-based Factor Activity Assaysmentioning

confidence: 99%

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Clinical utility and impact of the use of the chromogenic vs one‐stage factor activity assays in haemophilia A and B

Marlar

Strandberg

Shima

et al. 2019

European J of Haematology

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Treatment of haemophilia A/B patients comprises factor VIII (FVIII) or factor IX (FIX) concentrate replacement therapy, respectively. FVIII and FIX activity levels can be measured in clinical laboratories using one‐stage activated partial thromboplastin time (aPTT)‐based clotting or two‐stage chromogenic factor activity assays. We discuss strengths and limitations of these assays, providing examples of clinical scenarios to highlight some of the challenges associated with their current use for diagnostic and monitoring purposes. Substantial inter‐laboratory variability has been reported for one‐stage assays when measuring the activity of factor replacement products due to the wide range of currently available aPTT reagents, calibration standards, factor‐deficient plasmas, assay conditions and instruments. Chromogenic activity assays may avoid some limitations associated with one‐stage assays, but their regulatory status, perceived higher cost, and lack of laboratory expertise may influence their use. Haemophilia management guidelines recommend the differential application of one or both assays for initial diagnosis and disease severity characterisation, post‐infusion monitoring and replacement factor potency labelling. Efficient communication between clinical and laboratory staff is crucial to ensure application of the most appropriate assay to each clinical situation, correct interpretation of assay results and, ultimately, accurate diagnosis and optimal and safe treatment of haemophilia A or B patients.

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Section: One-stage Aptt-based Factor Activity Assaysmentioning

confidence: 99%

Section: One-stage Aptt-based Factor Activity Assaysmentioning

confidence: 99%

Clinical utility and impact of the use of the chromogenic vs one‐stage factor activity assays in haemophilia A and B

Marlar

Strandberg

Shima

et al. 2019

European J of Haematology

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“…8,9 In clinical practice, unwanted immune responses against FVIII or FIX are commonly identified as FVIII or FIX inhibitors using Bethesda or Nijmegen-modified Bethesda assays that assess the neutralizing capacity of FVIII-or FIX-specific antibodies. 10,11 Although this is vital information, testing solely for inhibitors is like uncovering the tip of the iceberg while the complexity of FVIII-or FIX-specific immune responses remains under the surface ( Figure 1). Antibodies are produced as a result of a cascade of tightly regulated interactions between different cells of the innate and adaptive immune system located in distinct compartments.…”

Section: Neutralizing Antibodies Against Fviii and Fix Are The Major mentioning

confidence: 99%

Risky business of inhibitors: HLA haplotypes, gene polymorphisms, and immune responses

Reipert

2014

Hematology

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The development of neutralizing antibodies against factor VIII (FVIII inhibitors) and factor IX (FIX inhibitors) is the major complication in hemophilia care today. The antibodies neutralize the biological activity of FVIII and FIX and render replacement therapies ineffective. Antibodies are generated as a result of a cascade of tightly regulated interactions between different cells of the innate and the adaptive immune system located in distinct compartments. Any event that modulates the repertoire of specific B or T cells, the activation state of the innate and adaptive immune system, or the migration pattern of immune cells will therefore potentially influence the risk for patients to develop inhibitors. This chapter reviews our current understanding of different pathways of antibody development that result in different qualities of antibodies. Potential differences in differentiation pathways leading to high-affinity neutralizing or low-affinity non-neutralizing antibodies and the potential influence of gene polymorphisms such as HLA haplotype, FVIII haplotype, and polymorphisms of immunoregulatory genes are discussed. Learning Objectives• To understand that FVIII and FIX inhibitors are only the tip of the iceberg: antibodies are generated as a result of a cascade of tightly regulated interactions between different cells of the innate and the adaptive immune system located in distinct compartments • To understand that any event that affects the activation state of the innate or the adaptive immune system, the repertoire of specific B or T cells, or the migration pattern of immune cells potentially influences the risk for patients to develop FVIII or FIX inhibitors Neutralizing antibodies against FVIII and FIX are the major challenge in replacement therapies for patients with hemophiliaThe development of neutralizing antibodies against factor VIII (FVIII inhibitors) and factor IX (FIX inhibitors) is the major complication in hemophilia care today. The antibodies neutralize the biological activity of FVIII and FIX and render replacement therapies ineffective. FVIII inhibitors develop in ϳ20%-32% of patients with severe hemophilia A (plasma FVIII activities Ͻ1%) and in ϳ3%-13% of patients with moderate (plasma FVIII activity 1%-5%) and mild (plasma FVIII activity 5%-25%) hemophilia A. 1,2 Recently, Eckardt et al 3 reported that the risk for patients with mild and moderate hemophilia A to form inhibitors increases with an increasing number of days of exposure to FVIII products and might be higher than anticipated.Most FVIII inhibitors bind to functionally important domains of FVIII and prevent its interaction with other coagulation factors such as factors IIa, IXa, and X and VWF or with phospholipids. 4 Other FVIII inhibitors have catalytic activities and hydrolyze the protein. 4 FIX inhibitors are seen less frequently than FVIII inhibitors. Their overall incidence is 1%-3% for all patients with hemophilia B treated with FIX products and 9%-23% for patients with severe hemophilia B who express plasma FIX activit...

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Section: Working Toward Answers To Unresolved Questionsmentioning

confidence: 99%

“…Firstly, problems with assay accuracy and interassay variability are ongoing and thought to be related to the inherent imprecision of the one-stage clotting assay [31]. Furthermore, there is still no international consensus on the lower limit of inhibitor detection and, consequently, the definition of a negative antibody titre by either the Bethesda or the Nijmegen assay [31]. In a further attempt to improve assay accuracy and define the lower limit of inhibitor detection, Verbruggen and colleagues have now proposed replacing immuno-depleted FVIII deficient plasma with 4% albumin in the control mixture [32].…”

Section: Working Toward Answers To Unresolved Questionsmentioning

confidence: 99%

Inhibitor treatment in haemophilias A and B: inhibitor diagnosis

DiMichele

2006

Haemophilia

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The clinical diagnosis and quantitative measurement of polyclonal IgG inhibiting antibodies are the subjects of this review. Inhibitors in congenital haemophilia are usually diagnosed either as part of a routine surveillance schedule or following a bleeding episode that responds poorly to standard specific replacement therapy. Routine surveillance schedules for paediatric haemophilia A patients during high-risk incidence periods are variable and the subject of ongoing discussion. There have never been any published recommendations for following haemophilia B patients at high risk for inhibitor development. The Factor VIII/IX Subcommittee of the International Society on Thrombosis and Haemostasis scientifically endorsed the Nijmegen method for inhibitor measurement in 1996. However, there are many unresolved issues surrounding inhibitor diagnosis using these assays. These issues include: (i) questions of accuracy and inter-assay variability inherent to the one-stage clotting assay; (ii) lack of consensus regarding the assay cut-off for negative determination; (iii) lack of assay standardization and (iv) the clinical importance of capturing non-neutralizing antibodies currently not measured in the functional assays. Ongoing efforts to resolve these issues will be discussed.

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Laboratory Assays in Hemophilia

Cited by 8 publications

References 25 publications

Clinical utility and impact of the use of the chromogenic vs one‐stage factor activity assays in haemophilia A and B

Clinical utility and impact of the use of the chromogenic vs one‐stage factor activity assays in haemophilia A and B

Risky business of inhibitors: HLA haplotypes, gene polymorphisms, and immune responses

Inhibitor treatment in haemophilias A and B: inhibitor diagnosis

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