Disorders of Plasma Clotting Factors and Transfusion Therapy PDF

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Summary

Coagulation Factor Deficiency- This deficiency can be caused by: o Decreased Synthesis o Abnormal Synthesis o Consumption/loss of coagulation factors o Inactivation of coagulation factors by inhibitors (antibodies) - A deficiency in coagulation factors results in a lack of fibrin clot. - Different b...

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MLSC-3121U, Clinical Hematology II Coagulation Factor Deficiency -

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This deficiency can be caused by: o Decreased Synthesis o Abnormal Synthesis o Consumption/loss of coagulation factors o Inactivation of coagulation factors by inhibitors (antibodies) A deficiency in coagulation factors results in a lack of fibrin clot. Different bleeding than primary hemostasis. Hemorrhages are in muscle tissue and joints and can be localize, acquired or congenital. Acquired Factor deficiency, seen in: o Liver Disease, the liver produces the coagulation factors so if it is not working properly than you will have less coagulation factors. Affects vitamin-K dependant factors and FV is a specific marker for liver disease. Thrombocytopenia or abnormal fibrinogen may be present. o Vitamin-K Deficiency, vitamin K is needed for factor activation so a lack in it will cause a deficiency in active factors. Antibiotics may cause this because bacteria that are needed to make vitamin-K die. o Renal Failure, may cause abnormal platelets and improper kidney function can cause the loss of factors into the urine. o Drug Use, aspirin increases bleeding tendency by affecting platelet function.

Tests for Secondary Hemostasis -

Prothrombin Time, tests the extrinsic pathway starting with factor VII. Activated Partial Thromboplastin Time, assesses the intrinsic pathway starting with factor XII. Mixing Study, done if PT and APTT are abnormal. Patient plasma is mixed with normal plasma containing everything needed for clotting. If the patient is deficient in a factor, the normal plasma in equal amount will provide enough factor for normal clotting to happen in PT or APTT. If the sample does improve with a mixing study, it is indicative of a factor deficiency since the sample needed help clotting from the normal plasma. There are some inhibitors (antibodies) that affect clotting factors that take time to act, so lack of correction with normal serum after 2 hours is reflective of an inhibitor.

Coagulation Factors Factor I (Fibrinogen) -

Large protein made in the liver and accounts for the most volume in the plasma. Has a long half-life and is made of pairs of alpha, beta and gamma chains joined by disulphide bonds. Thrombin cleaves peptides A and B from the alpha and beta chains

MLSC-3121U, Clinical Hematology II

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causing the monomers to form an unstable clot. Factor XIII makes the clot stable and insoluble. Afibrinogenemia, absence of fibrinogen activity and antigen in plasma. Prolongation of clot time or lack of formation is seen in the lab. Mixing studies should correct the issue and a Factor I assay would be low. Best treatment is cryoprecipitate because it provides the highest concentration of fibrinogen with the smallest amount of volume. Hypofibrinogenemia, a heterozygous autosomal recessive disorder. Lab tests show prolongation of clot times (not as long as afibrinogenemia) and a Fibrinogen assay will produce a low value. Treated with cryoprecipitate. Dysfibrinogenemia, abnormal Factor I protein produced. Results in defective clotting and fibrinolysis. Lab tests show prolonged PT, APTT and bleeding time (BT) along with abnormal clottable fibrinogen activity with high levels of thrombin. Treatment is cryoprecipitate. o Reptilase Time (RT), uses a thrombin-like enzyme from snakes that only cleaves fibrinopeptide A. It is not affected by heparin or antithrombin and is prolonged in dysfibrinogenemia. Hyperfibrinogenemia, fibrinogen is an acute phase reactant, so plasma levels can increase extremely high following injury, pregnancy or infections. Can be misleading in patients with low fibrinogen since injury/physical stress can raise the patient’s low level to a normal level.

Factor II (Prothrombin) -

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Most abundant vitamin K dependant coagulation factor. Hypoprothrombinemia, can be inherited or acquired. Lab findings include prolonged PT and APTT while mixing studies will correct this. Treatment includes a prothrombin complex concentrate (containing FII, VII, IX and X). Dysprothrombinemia, can be inherited or acquired. Structural defect leads to decreased functionality of prothrombin. Lab findings are similar to hypo and treatment involves prothrombin complex concentrate. Prothrombin G 20210 A Mutation, point mutation in the prothrombin gene and is the second most common cause of inherited thrombophilia. Detected using PCR testing and generally restricted to Caucasians.

Factor V (Proaccelerin) -

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Synthesized in the liver and is not very stable. Will rapidly inactivate in plasma kept at room temperature. Deficiency lab findings include prolonged PT and APTT and clotting is corrected with a mixing study. Treatment includes fresh frozen plasma because there is not enough factor V in the cryoprecipitate. Causes parahemophilia. Factor V Leiden Mutation, FVa and FVIIIa are inactivated by Activated Protein C (APC) under normal conditions to prevent ongoing thrombin generation. APC Resistance is a

MLSC-3121U, Clinical Hematology II molecular defect in the FV gene. Loss of APC cleavage leads to a decreased inactivation of FVa by APC, continued thrombin generation and increased risk of thrombosis. o Viper Venom Test. Compares clot times with and without APC. Normal patients have normal clot times without added APC compared to when they have added APC. APC resistant patients will have shorter clot times for both tests because the patient FV factor resists APCs ability to inactivate FVa and FVIIIa to stop clotting. Factor VII (Proconvertin) -

Made in the liver and requires vitamin K for activation. Forms an extrinsic tenase complex with tissue factor to activate FX to FXa and FIX to FIXa, thus bypassing contact activation of FXI and FXII. Homozygous Congenital FVII Deficiency, rare autosomal recessive disorder. Causes deep muscle hematomas and cerebral hemorrhage. Lab findings include prolonged PT with a normal APPT (factor VII is involved in the extrinsic system, which is tested by PT). Corrects with a mixing study and treated with prothrombin complex concentrate.

Factor VIII (Antihemophilic Factor) -

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FVIII:C, small protein of FVIII that is functionally active and responsible for clotting (C=clotting). FVIII:C and vWF form a complex that mediates platelet adhesion, stabilizes FVIII:C and protects FVIII:C from degradation. Also concentrates FVIII:C at site of injury. FVII:C Deficiency (Hemophilia A), inherited sex linked recessive disorder. Second most frequently inherited bleeding disorder. Can be due to a molecular defect to the FVIII gene. Males with the affected X chromosome manifest the disease while women are carriers if they have one affected X chromosome. o Severe Hemophiliacs, FVIII less than 1%. o Moderately Severe Hemophiliacs, 2-5% FVIII. o Mild Hemophiliacs, 5-30% FCVIII. Test results for Hemophilia A include prolonged APTT, normal PT and BT, low/absent FVIII:C and a normal vWF:Ag and platelet function. Treatment includes human plasma FVIII:C (up until 1984 due to possible infection) and synthetic recombinant human FVII:C (modern treatment used). 10-15% of Hemophilia A patients develop antibodies against FVIII:C. As a result, a Bethesda assay is done to determine the activity of the inhibitor. People with really high inhibition will be switched to a non-human porcine FVIII:C. von Willebrand Disease (vwD), is inherited as an autosomal dominant disorder. Most common inherited bleeding disorder and causes prolonged bleeding times due to mutation in the vWF gene. Causes bleeding in mucosal tissue unlike Hemophilia A which causes mostly deep muscle bleeding. vwD is caused by a mutation in the vwF gene resulting in quantitative or qualitative vwF deficiencies. Can present with a prolonged APTT and corrects with a mixing study. Platelets are normal but cannot attach due to the problems with vwF.

MLSC-3121U, Clinical Hematology II -

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Acquired vwD (AvWD), rare bleeding disorder that generally affects the elderly. Presents with various bleeding symptoms and is identical to vwD except it is not caused by genetics. AvWD is associated with: o Monoclonal Gammopathies o Lymphoma or Leukemia o Cardiac Defects o Systemic Lupus Erythematosus Lab findings include variable APTT, decreased vwF activity, normal antigen, variable FVIII:C and vWF:Ag, prolonged BTs and a loss of HMW multimers. Symptoms include moderate/severe mucosal bleeding and treatment involves DDAVP injections (causes endothelial cells to release more vWF). Ristocethin-Induced Platelet Agglutination Assay, an aggregometer test used to qualitatively evaluate the vWF-platelet interaction through the binding of Gp1b. The vWF antigen is measured by ELISA testing, rocket immunoelectrophoresis or automated method using vWF coated latex beads. Bleeding Time (BT), the assessment of platelet-vWF interaction. A CBC is needed to do this because if the platelet count is low, you know that the BT will be high. The test just tells you that there is a problem in primary hemostasis. Not routinely done anymore. Platelet Function Analyzer, replaces the BT test to avoid scarring on patients and patient variability. Two cartridges with the membrane coated with collagen and epinephrine or collagen and ADP are used. Measures the time for platelets to occlude the aperture in the membrane (closure time, CT). Multimer Analysis, evaluates the multimer structure of vwF because it is made of many multimers. Separates the multimers out through electrophoresis to evaluate the structure of vWF. Quantitative defects are seen as weak staining bands and qualitative defects are seen as missing bands.

Factor IX (Christmas Factor, Plasma Thromboplastin Component) -

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Single chain glycoprotein coded by a gene on the X chromosome. FVIII with or without thrombin cannot activate FX without FIXa. Factor IX Deficiency (Hemophilia B), sex linked disorder that affects males. Severe hemophilia B occurs in less than 1% patients and is caused by the total absence of FIX activity and antigen. Symptoms are identical to Hemophilia A. Lab findings include normal PT and BT, prolonged APTT (FIX is only in the intrinsic pathway) and correction in a mixing study. Treatment is purified FIX concentrate.

Factor X (Stuart-Prower Factor) -

Vitamin K activated protein synthesized in the liver. Composed of heavy and light chains linked by a disulphide bond.

MLSC-3121U, Clinical Hematology II -

Factor X Deficiency, rare autosomal recessive bleeding disorder. Lab findings include prolonged PT and APTT (Factor X is in the common pathway), correction through mixing study, normal TT and BT and prolonged Russel’s viper venom time. Treatment is prothrombin complex concentrate.

Factor XI (Plasma Thromboplastin Antecedent) -

Glycoprotein produced in the liver. Circulates in complex with HMW kininogen. Contact activation with negative surfaces leads to FXIIa cleavage to form FXIa. Factor XI Deficiency (Hemophilia C), inherited as an autosomal recessive trait prevalent in the Ashkenazi Jewish population. Symptoms include mild to severe bleeding. Lab findings include prolonged APTT, normal PT and correction through mixing studies. Fresh frozen plasma is treatment.

Factor XII (Hageman Factor) -

Single chain b eta-globulin synthesized in the liver by a gene on chromosome 5. It is a factor of the contact activation pathway and starts off the intrinsic pathway. Symptoms include an increased risk of thrombosis. Lab findings include normal PT and a prolonged APTT (Factor XII starts the intrinsic pathway).

Factor XIII (Fibrin-Stabilizing Factor) -

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Circulates with fibrinogen with a half-life of one week. Is not involved in the coagulation cascade leading to the fibrin clot. It stabilizes the fibrin clot through cross linking when it is activated by thrombin. Symptoms include poor wound healing. Lab findings include fibrin clots of affected patients lysing in 5M urea within 24 hours. Treatment involves FXIII concentrates.

Prekallikrein (PK, Fletcher Factor) -

Single chain protein synthesized by the liver. It is an important mediator of inflammation, converts plasminogen into plasmin and activates complement C3 and C5. Prekallikrein Deficiency, asymptomatic disorder. Lab findings include prolonged APTT that corrects with mixing studies. Treatment is usually not done since it does not associate with a bleeding risk.

High Molecular Weight Kininogen (Fitzgerald Factor) -

Single chain glycoprotein synthesized by the liver and involved in contact activation. Rare and autosomal recessive.

MLSC-3121U, Clinical Hematology II -

High Molecular Weight Kininogen Deficiency (HMWD), asymptomatic disorder that is not associated with bleeding. Lab findings include prolonged APTT and correction with mixing studies.

Coagulation Inhibitors -

Acquired inhibitors develop in patients with underlying disorders and can impact hemostasis and coagulation factor testing.

Specific Inhibitors -

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An antibody that inhibits a single factor’s activity or lead to increased clearance. FVIII:C Inhibitors, the most common. These are usually IgG autoantibodies that ultimately cause acquired hemophilia. Shows normal PT, prolonged APTT and does not correct with mixing studies since FVIII:C is only inhibited and not missing. Bethesda Inhibitor Assay, used to quantitate inhibitor titre in patient plasma. Dilutions of patient plasma are mixed with equal volumes of normal plasma. The mixture is incubated for 2 hours at 37 degrees with normal plasma diluted with equal volume of buffer as control. This is specialized testing and not routinely done. Treatment for patients with specific inhibitors has the primary goal of stabilizing hemostasis. Patients with low inhibitor titres with no increase after additional factor are treated with really high levels of factor. This will overwhelm the autoantibodies by saturating all their bindings sites with factor left over to work uninhibited. Patients with higher antibody titres with an increase in titre after additional FVIII:C are difficult to treat. Treatment mainly involves immunosuppressive drugs to stop the production of autoantibodies or trying to remove them directly.

Non-Specific Inhibitors -

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Block action of phospholipids of multiple clotting reagents. Lupus Anticoagulants (LAC), antibodies (IgG and/or IgM) that inhibit activity of phospholipids in PT or APTT reagents (not coagulation factors). This is an acquired antibody. Patient plasma with LAC antibodies have prolonged APTT without correction through mixing studies (Ab works on reagents not factors) and a normal PT (PT reagent has a lot more phospholipids and resists inhibitors). Diluted Russel’s viper venom time can test for LAC.

MLSC-3121U, Clinical Hematology II Transfusion Therapy Indication of Platelets -

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Active bleeding is attributed low platelets (thrombocytopenia) or abnormally functioning platelets (thrombocytopathy). Platelets transfusions are not usually indicated for patients with: o ITP, idiopathic thrombopenic purpura caused by increased destruction. o TTP, thrombotic thrombocytopenic purpura. o DIC, disseminated intravascular coagulation from increased platelet consumption. o HUS, hemolytic uremic syndrome. 1 unit of random platelets should raise the adult platelet count by 5 to 10 x10^9/L. A failure to achieve this expected increase may indicate platelet refractoriness.

Plasma -

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Plasma is usually used to treat simple or multiple coagulation deficiencies. FFP, prepared from whole blood that has been separated. Contains maximum levels of both stable and labile clotting factors (1 IU/mL) and about 400mg of fibrinogen and 1 unit/mL activity of Factors V and VIII. Frozen Plasma 24, contains all stable proteins, normal levels of factor V and slightly reduced levels of factor VIII. These types of plasma are usually used to treat liver failure, DIC, vitamin K deficiency, warfarin overdose or massive transfusion. These products should not be used as blood volume expanders because safer options are now available. Cryoprecipitate Reduced Plasma, prepared from FFP after it has been thawed and centrifuged to prepare cryoprecipitate. In the process, factor VIII, vWF, cryoglobulins and fibronectin are removed, leaving only albumin, factors II, V, IX, X, XI and ADAMTS13. Cryoprecipitate is used to replace factor VIII, vWF, fibrinogen, fibrinonectin and factor XIII. Each bag should contain at least 150mg of fibrinogen and can be used as a fibrin sealant. Usually used for transfusion or plasma exchange in TTP patients and cannot be used instead of FFP, FP24 or thawed plasma because it lacks factor VIII. Thawed and Liquid Plasma, made from FFP that has been stored 1-5 days after thawing. Contains decreased amounts of factor V and VIII and should not be used to replenish these factors in deficiencies. Useful for treatment of Warfarin overdose or reversal or factor XI deficiency. Can also be used for plasma exchange for TTP, HUS or HELLP patients. Factor VIII, this product usually treats patients with hemophilia A or factor VIII deficiency. Only factor VIII with vWF can be used to treat patients with von Willebrand’s disorder.

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There are two forms of factor VIII, plasma-derived (pooled screened donor plasma) and recombinant (biotechnology). Factor IX, prepared from pooled plasma and used to treat patients with hemophilia B or factor IX, VII, and X deficiency. There are three forms of factor IX, prothrombin complex (significant levels of vitamin K dependant factors), factor IX (FIX, less thrombogenic than prothrombin complex) and recombinant FIX. Factor XIII, treats FXIII and severe autosomal bleeding disorders. Anti-Thrombin Concentrate, treats patients with hereditary deficiency of anti-thrombin. Recombinant Human Activated Factor VII, treats patients with a variety of bleeding disorders....