The responsiveness of different APTT reagents to mild factor VIII, IX and XI deficiencies.
Summary of "The responsiveness of different APTT reagents to mild factor VIII, IX and XI deficiencies."
Introduction:â€‚ The sensitivity of APTT reagents to deficiencies of factors VIII, IX, XI and XII varies because of their composition. The APTT is used as a screening test for these factors, and a deficiency should manifest with a prolongation to the APTT, which may trigger the need for specific factor assays to be performed. Methods:â€‚ The suitability of APTT reagents to detect mild deficiencies can be assessed by the analysis of the APTT of plasma, which has an increasing concentration of the factor in question. The APTT responsiveness can be determined from the intersection of the curve and the upper limit of the APTT normal reference range for that APTT reagent. We assessed the APTT responsiveness (in U/dl) to factors VIII, IX and XI of four APTT reagents; Actin FS (Siemens), Synthasil (IL), STA-PTTA (Stago) and Dapttin (Technoclone). Results:â€‚ Synthasil was the most sensitive reagent to mild reductions of factors VIII and XI, whilst Actin FS was the most sensitive for FIX. STA-PTTA showed less sensitivity than Synthasil and Actin FS; Dapttin was insensitive to mild deficiencies of factors IX and XI and should not be used as a screening test. Conclusion:â€‚ Both Synthasil and Actin FS are acceptable reagents to screen for reduced factors VIII, IX and XI, and the number of mildly reduced factors not diagnosed will be limited.
Sheffield Haemophilia and Thrombosis Centre, Sheffield, UK Division of Cardiovascular Science, University of Sheffield, Sheffield, UK.
This article was published in the following journal.
Name: International journal of laboratory hematology
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/20840376
- DOI: http://dx.doi.org/10.1111/j.1751-553X.2010.01261.x
Medical and Biotech [MESH] Definitions
Blood-coagulation factor VIII. Antihemophilic factor that is part of the factor VIII/von Willebrand factor complex. Factor VIII is produced in the liver and acts in the intrinsic pathway of blood coagulation. It serves as a cofactor in factor X activation and this action is markedly enhanced by small amounts of thrombin.
Activated form of factor VIII. The B-domain of factor VIII is proteolytically cleaved by thrombin to form factor VIIIa. Factor VIIIa exists as a non-covalent dimer in a metal-linked (probably calcium) complex and functions as a cofactor in the enzymatic activation of factor X by factor IXa. Factor VIIIa is similar in structure and generation to factor Va.
Storage-stable blood coagulation factor acting in the intrinsic pathway. Its activated form, IXa, forms a complex with factor VIII and calcium on platelet factor 3 to activate factor X to Xa. Deficiency of factor IX results in HEMOPHILIA B (Christmas Disease).
Collagen Type Viii
A non-fibrillar collagen originally found in DESCEMET MEMBRANE. It is expressed in endothelial cell layers and in tissues undergoing active remodeling. It is heterotrimer comprised of alpha1(VIII) and alpha2(VIII) chains.
Von Willebrand Factor
A high-molecular-weight plasma protein, produced by endothelial cells and megakaryocytes, that is part of the factor VIII/von Willebrand factor complex. The von Willebrand factor has receptors for collagen, platelets, and ristocetin activity as well as the immunologically distinct antigenic determinants. It functions in adhesion of platelets to collagen and hemostatic plug formation. The prolonged bleeding time in VON WILLEBRAND DISEASES is due to the deficiency of this factor.
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