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Commonly used tests of hemostasis provide the initial screening for clotting factor activity (Fig. 110-1), and disease phenotype often correlates with the level of clotting activity. An isolated abnormal prothrombin time (PT) suggests FVII deficiency, whereas a prolonged activated partial thromboplastin time (aPTT) indicates most commonly hemophilia or FXI deficiency (Fig. 110-1). The prolongation of both PT and aPTT suggests deficiency of FV, FX, FII, or fibrinogen abnormalities. The addition of the missing factor to the subject's plasma at a range of doses will correct the abnormal clotting times; the result is expressed as percent of the activity observed in. | Chapter 110. Coagulation Disorders Part 2 Commonly used tests of hemostasis provide the initial screening for clotting factor activity Fig. 110-1 and disease phenotype often correlates with the level of clotting activity. An isolated abnormal prothrombin time PT suggests FVII deficiency whereas a prolonged activated partial thromboplastin time aPTT indicates most commonly hemophilia or FXI deficiency Fig. 110-1 . The prolongation of both PT and aPTT suggests deficiency of FV FX FII or fibrinogen abnormalities. The addition of the missing factor to the subject s plasma at a range of doses will correct the abnormal clotting times the result is expressed as percent of the activity observed in normal subjects. Figure 110-1 Boumi Ftuo A5. K f p r PL. Bnunwtld E. H Ui r SL. Lonsû OL. Jirnttori JL. Lofiilîo Jl Coagulation cascade and laboratory assessment of clotting factor deficiency by activated partial prothrombin time aPTT prothrombin time PT . and thrombin time TT . Acquired deficiencies of plasma coagulation are more frequent than congenital disorders the most common disorders include hemorrhagic diathesis of liver disease disseminated intravascular coagulation DIC and vitamin K deficiency. In these disorders blood coagulation is hampered by the deficiency of more than one clotting factor and the bleeding episodes result from perturbation of both primary e.g. platelet and vessel wall interactions and secondary coagulation hemostasis. The development of antibodies to coagulation plasma proteins clinically termed inhibitors is a relatively rare problem that most often affects hemophilia A or B and FXI-deficient patients who receive repeated doses of the missing protein to control bleeding episodes. Inhibitors also occur among subjects without genetic deficiency of clotting factors for example in the postpartum setting as a manifestation of underlying autoimmune or neoplastic disease or idiopathically. Rare cases of inhibitors to thrombin or FV have been reported in .
